JP7602249B2 - Electrostatic deposition equipment - Google Patents

Description

The present invention relates to an electrostatic film forming device that adheres powders, such as edible powders and functional powders, to a target object using electrostatic force.

Electrostatic screen printing devices are used for a variety of purposes, such as printing on food products and manufacturing industrial products. The principle of electrostatic printing will be explained with reference to FIG. 6. As shown in FIG. 6, an electrostatic screen printing device includes a conveyor 201 on which an object 200 is placed, a screen 202 having a mesh, and a roll brush 203 on the screen 202. The object 200 is moved by the conveyor 201 to a printing position below the screen 202.

The screen 202 is connected to the negative pole of a DC power source, and the conveyor 201 is connected to the positive pole of the DC power source and is also grounded. A high voltage is applied between the screen 202 and the conveyor 201 by the DC power source, which creates an electrostatic field between the screen 202 and the object 200 on the conveyor 201. The powder is supplied from the hopper 204 onto the rotating roll brush 203 and falls onto the screen 202. The powder on the screen 202 is rubbed into the mesh of the screen 202 by the rotating roll brush 203, and is pushed out through the mesh to the bottom of the screen 202. At this time, the powder is negatively charged by friction with the rotating roll brush 203. Therefore, the powder is attracted to the grounded object 200 and adheres to the surface of the object 200, forming a film of uniform thickness on the object 200.

This type of electrostatic printing technology is capable of forming uniform powder films, and so it has recently begun to be used in the manufacture of a variety of industrial products, including fuel cells, all-solid-state batteries, secondary batteries, and cosmetics.

JP 2002-347221 A

As electrostatic printing is performed, powder may gradually accumulate on the underside of the screen 202. More specifically, the powder rubbed into the mesh of the screen 202 by the roll brush 203 flies toward the target object 200, but some of the powder does not head toward the target object 200 and instead adheres to the underside of the screen 202. As electrostatic printing is performed, such powder gradually forms lumps on the underside of the screen 202 and eventually falls onto the target object 200 due to its own weight.

However, the powder lumps that fall under their own weight are large in size, which causes the thickness of the powder film formed on the target object 200 to be uneven. As a result, this can reduce product yields or even cause product defects.

Therefore, the present invention provides an electrostatic film forming device that can prevent powder from accumulating on the underside of the screen.

In one aspect, an electrostatic film-forming device that deposits powder onto an object by electrostatic force is provided, the electrostatic film-forming device comprising a screen arranged facing the object, a rubbing roller that rubs the powder into the screen, a roller rotation mechanism that rotates the rubbing roller around its axis, a power source that applies a voltage between the screen and the object, and a striking device having a hammer that intermittently strikes the screen.

In one aspect, the striking device further comprises an adjustment device configured to adjust the strength of the strike applied by the hammer to the screen.
In one embodiment, the frequency of the strikes applied by the hammer to the screen is synchronized with the rotation speed of the scrubbing roller.
In one aspect, the hammer is arranged to strike the screen in a longitudinal direction.
In one aspect, the striking device includes a spring that urges the hammer towards the screen.
In one embodiment, the impact device has a cam follower connected to the hammer and a circular cam rotatable integrally with the rubbing roller.
In one embodiment, the adjustment device further includes a support member that supports an end of the spring, and a position adjustment mechanism that adjusts the position of the support member.

According to the present invention, the hammer strikes the screen intermittently, so that the powder lumps formed on the underside of the screen can be periodically dropped from the screen. In other words, the hammer can apply a relatively large impact to the screen, so that the powder lumps can be dropped by their own weight. The reason for applying the strikes intermittently is that by striking the screen after the powder has formed a relatively large lump, the powder lumps can be dropped by their own weight. Experiments have confirmed that fine vibrations, instead of hammer strikes, make it difficult for the powder lumps to fall. Furthermore, vibrations cause the entire device to resonate, causing malfunctions in the device. Therefore, hammer strikes are more effective than vibrations. Furthermore, according to the present invention, a mechanism such as a wiper for wiping the underside of the screen is not required.

The ease with which powder lumps fall also depends on the type of powder. According to the present invention, the adjustment device can adjust the strength of the impact independently of the impact period. Thus, the hammer can deliver an impact of appropriate strength to the screen depending on the type of powder.

1 is a front view showing an embodiment of an electrostatic deposition apparatus. FIG. 2 is a side view of the electrostatic deposition apparatus shown in FIG. FIG. 4 is a schematic diagram showing details of an impact device. Figure 4(a) is a diagram showing the circular cam and cam follower as viewed from the direction indicated by arrow A in Figure 3, Figure 4(b) is a diagram showing the circular cam and cam follower as viewed from the direction indicated by arrow B in Figure 3, and Figure 4(c) is an exploded view of the circular cam. FIG. 2 is a top view of the screen and hammer. FIG. 1 is a diagram illustrating the principle of electrostatic printing.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing one embodiment of an electrostatic film forming apparatus, and FIG. 2 is a side view of the electrostatic film forming apparatus shown in FIG. 1. The electrostatic film forming printing apparatus includes a screen 10 arranged above an object 1, a cylindrical rubbing roller 12 placed on the screen 10, a hopper 14 that supplies powder to the rubbing roller 12, and a power source DC that applies a voltage between the screen 10 and the object 1. Examples of powder include edible powder and functional powder. The object 1 is not particularly limited and may be food, or industrial products such as fuel cells, all-solid-state batteries, secondary batteries, and cosmetics.

The screen 10 is disposed facing the object 1, and the screen 10 and the object 1 are not in contact with each other. As shown in FIG. 1, the screen 10 is disposed horizontally at a position above the object 1. The screen 10 is formed with mesh 11 through which the powder passes. The powder is rubbed into the mesh 11 of the screen 10 by the outer circumferential surface of the rubbing roller 12.

The material of the rubbing roller 12 is soft open-cell urethane sponge, which has good rubbing properties for powder into the screen 10. As shown in FIG. 2, the rubbing roller 12 is connected to a roller rotation mechanism 19. The rubbing roller 12 is rotated by the roller rotation mechanism 19 around its axis extending parallel to the screen 10, and the outer circumferential surface of the rubbing roller 12 is brought into sliding contact with the mesh 11 of the screen 10. The roller rotation mechanism 19 is composed of a motor and a torque transmission mechanism (e.g., a sprocket, a chain, etc.). The roller rotation mechanism 19 may be composed of a motor directly connected to the rubbing roller 12.

The hopper 14 is disposed above the screen 10 and the rubbing roller 12. The hopper 14 comprises a hopper box 20 that contains powder therein, a hopper brush 22 disposed inside the hopper box 20, and a brush rotation mechanism 24 that rotates the hopper brush 22. The brush rotation mechanism 24 is composed of a motor and a torque transmission mechanism (e.g., a sprocket, a chain, etc.). The brush rotation mechanism 24 may be composed of a motor directly connected to the hopper brush 22.

The hopper brush 22 is placed on the bottom of the hopper box 20. A number of holes (not shown) are formed in the bottom of the hopper box 20. When the brush rotation mechanism 24 rotates the hopper brush 22, the powder in the hopper box 20 is agitated by the hopper brush 22 and pushed into the holes in the bottom of the hopper box 20, and passes through these holes to be supplied to the outer circumferential surface of the rubbing roller 12. The amount of powder supplied to the rubbing roller 12 can be adjusted by the rotation speed of the hopper brush 22. In one embodiment, the hopper 14 may supply the powder onto the screen 10.

A conveyor 2 is disposed below the screen 10 to transport multiple objects 1 horizontally. The conveyor 2 moves the objects 1 sequentially 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 pole of a power supply (voltage application device) DC, and the conveyor 2 is connected to the positive pole of the power supply DC. The positive pole of the power supply DC and the conveyor 2 are grounded. A high voltage is applied between the screen 10 and the conveyor 2 by the power supply DC, which creates an electrostatic field between the screen 10 and the objects 1 on the conveyor 2.

The powder is supplied from a hopper 14 onto the rubbing roller 12 and is carried to the screen 10 by the rotating rubbing roller 12. The powder is rubbed into the mesh 11 of the screen 10 by the rotating rubbing roller 12 and pushed out to the bottom of the screen 10. At this time, the powder is negatively charged by friction with the rotating rubbing roller 12. Therefore, the powder is attracted to the grounded object 1 and adheres to the surface of the object 1, forming a film of uniform thickness on the object 1. It is preferable to oscillate the rubbing roller 12 in its axial direction by an oscillating mechanism (not shown) while rubbing the powder into the screen 10. Some types of powder are positively charged when rubbed into the mesh 11 of the screen 10 by the rubbing roller 12. When using such powder, the screen 10 is connected to the positive pole of a power source DC, and the negative pole of the power source DC and the conveyor 2 are grounded.

As shown in FIG. 2, the electrostatic printing device is equipped with an impact device 30 having a hammer 31 that intermittently impacts the screen 10. This impact device 30 is provided to remove powder lumps formed on the underside of the screen 10.

The impact device 30 will be described in detail below with reference to FIG. 3. The impact device 30 has a spring 35 that pushes the hammer 31 toward the screen 10, a cylinder 36 that houses the spring 35, and a hammer rod 38 to which the hammer 31 is fixed. The cylinder 36 is fixed to a bracket 40. The rotating shaft 13 of the rubbing roller 12 is also rotatably supported by the bracket 40. Most of the hammer rod 38 is located inside the cylinder 36.

The impact device 30 is equipped with a piston 43 fixed to a hammer rod 38. The piston 43 is disposed in a cylinder 36 and is movable together with the hammer rod 38 within the cylinder 36. One end of a spring 35 is in contact with the piston 43. The force of the impact that the hammer 31 applies to the screen 10 is provided by the spring 35, and the magnitude of the impact of the hammer 31 depends on the elasticity (stretching force) of the spring 35. The hammer 31 is made of a hard insulating material. For example, the hammer 31 is made of a hard insulating resin such as MC nylon, which is an engineering plastic.

The impact device 30 further includes an adjustment device 45 configured to adjust the strength of the impact that the hammer 31 applies to the screen 10. The adjustment device 45 further includes a support member 47 that supports an end of the spring 35, and a position adjustment mechanism 50 that adjusts the position of the support member 47. At least a portion of the support member 47 is disposed within the cylinder 36. One end of the spring 35 is supported by the piston 43, and the other end of the spring 35 is supported by the support member 47. The elastic force (stretching force) of the spring 35 is received by the piston 43 and the support member 47.

The position adjustment mechanism 50 has a screw 52 that extends through a slot 51 formed in the wall of the cylinder 36. The slot 51 has a shape that extends in the longitudinal direction of the hammer rod 38 and the cylinder 36. The screw 52 is screwed through the slot 51 into a threaded hole 55 of the support member 47. When the screw 52 is tightened, the relative position of the support member 47 with respect to the cylinder 36 is fixed, and when the screw 52 is loosened, the support member 47 becomes movable in the longitudinal direction of the cylinder 36. Since the end of the spring 35 is supported by the support member 47, the force of the spring 35, i.e., the strength of the impact of the hammer 31, can be adjusted by changing the position of the support member 47 in the longitudinal direction of the cylinder 36. However, the specific configuration of the position adjustment mechanism 50 is not limited to this embodiment, and other configurations may be used as long as the position of the support member 47 can be changed.

The impact device 30 has a cam follower 65 connected to the hammer 31 and a circular cam 61 that can rotate together with the rubbing roller 12. The cam follower 65 is in contact with the circular cam 61. The cam follower 65 is connected to the hammer 31 via the hammer rod 38 and the connecting rod 68. The cam follower 65 has a rotatable roller and is in rolling contact with the circular cam 61. The spring 35 presses the cam follower 65 against the circular cam 61 via the piston 43, the hammer rod 38, and the connecting rod 68. The circular cam 61 is fixed to the rotation shaft 13 of the rubbing roller 12 and rotates together with the rubbing roller 12. In this embodiment, the circular cam 61 is fixed to the rotation shaft 13 of the rubbing roller 12, but in one embodiment, the circular cam 61 may be connected to the rotation shaft 13 of the rubbing roller 12 via a torque transmission mechanism such as a gear.

Figure 4(a) shows the circular cam 61 and cam follower 65 as viewed from the direction indicated by arrow A in Figure 3, Figure 4(b) shows the circular cam 61 and cam follower 65 as viewed from the direction indicated by arrow B in Figure 3, and Figure 4(c) is an exploded view of the circular cam 61. The circular cam 61 has an inclined surface 62 inclined with respect to the movement direction CL of the hammer 31, and a vertical surface 63 parallel to the movement direction CL of the hammer 31. The inclined surfaces 62 and the vertical surfaces 63 are arranged alternately along the circumferential direction of the circular cam 61.

The cam follower 65 rolls into contact with the inclined surface 62, causing the position of the cam follower 65 to change along the movement direction CL of the hammer 31. Such a change in the position of the cam follower 65 compresses the spring 35 and can also release the compression of the spring 35. That is, when the cam follower 65 is in contact with the inclined surface 62, the piston 43 compresses the spring 35, and when the cam follower 65 leaves the inclined surface 62, the compression of the spring 35 is released and the spring 35 forcefully pushes the hammer 31 towards the screen 10 via the piston 43 and the hammer rod 38. As a result, the hammer 31 can strike the screen 10.

According to this embodiment, the compression and release of the spring 35 alternate with the rotation of the rubbing roller 12. Therefore, the period of the impact that the hammer 31 applies to the screen 10 is synchronized with the rotation speed of the rubbing roller 12. In this embodiment, the circular cam 61 has four inclined surfaces 62 and four vertical surfaces 63, so that the hammer 31 applies impact to the screen 10 four times during one rotation of the rubbing roller 12. However, the present invention is not limited to this embodiment. During one rotation of the rubbing roller 12, it is sufficient that the hammer 31 applies impact to the screen 10 at least once. In other words, it is sufficient that the circular cam 61 has at least one inclined surface 62 and at least one vertical surface 63. For example, the circular cam 61 may have one inclined surface 62 and one vertical surface 63, or may have multiple inclined surfaces 62 and multiple vertical surfaces 63.

By having the hammer 31 strike the screen 10 intermittently, the powder lumps formed on the underside of the screen 10 can be periodically dropped from the screen 10. In other words, the hammer 31 can apply a relatively large impact to the screen 10, so that the powder lumps can be dropped by their own weight. The reason for applying strikes intermittently is that by striking the screen 10 after the powder has formed a relatively large lump, the powder lumps can be dropped by their own weight.

The ease with which the powder lumps fall also depends on the type of powder. The adjustment device 45 can adjust the strength of the impact independently of the impact period. Thus, the hammer 31 can deliver an impact of appropriate strength to the screen 10 depending on the type of powder.

The growth rate of the powder lumps formed on the underside of the screen 10 is roughly proportional to the rotation speed of the rubbing roller 12. According to this embodiment, the hammer 31 can strike the screen 10 at a period synchronized with the rotation speed of the rubbing roller 12, so that the powder lumps formed on the underside of the screen 10 can be dropped before they become too large.

Figure 5 is a top view of the screen 10 and the hammer 31. As shown in Figure 5, the screen 10 has a rectangular shape extending along the axial direction of the rubbing roller 12. The hammer 31 is positioned so as to strike the screen 10 in the longitudinal direction. That is, the hammer 31 is positioned opposite the side of the screen 10, and strikes the screen 10 in the horizontal direction. This positioning of the hammer 31 allows the impact to be transmitted uniformly and instantly throughout the screen 10, allowing all of the powder lumps formed on the underside of the screen 10 to fall.

In the embodiments described so far, the impact device 30 has a combination of the cam 61 and the cam follower 65, but is not limited to the above embodiments as long as the hammer 31 can periodically impact the screen 10. For example, the impact device 30 may be configured to include an electromagnet instead of the cam 61 and the cam follower 65 and compress the spring 35 with the electromagnet. In another example, the impact device 30 may be configured to include an air cylinder instead of the cam 61 and the cam follower 65 and compress the spring 35 with the air cylinder. In yet another example, the impact device 30 may be configured to include an air cylinder instead of the spring 35, the cam 61, and the cam follower 65 and to impact the screen 10 with the hammer 31 fixed to the rod of the air cylinder. The strength of the impact that the hammer 31 applies to the screen 10 can be adjusted by the pressure of the gas supplied to the air cylinder.

The impact device 30 having the combination of the cam 61 and cam follower 65 described in the above embodiment has the advantage of being simpler in structure and having a longer service life than impact devices equipped with electromagnets or air cylinders.

The above-described embodiments have been described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical ideas of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical ideas defined by the scope of the claims.

REFERENCE SIGNS LIST 1 Object 2 Conveyor 10 Screen 11 Mesh 12 Rubbing roller 13 Rotating shaft 14 Hopper 19 Roller rotation mechanism 20 Hopper box 22 Hopper brush 24 Brush rotation mechanism 30 Impact device 31 Hammer 35 Spring 36 Cylinder 38 Hammer rod 40 Bracket 43 Piston 45 Adjustment device 47 Support member 50 Position adjustment mechanism 51 Slot 52 Screw 55 Screw hole 61 Circular cam 62 Inclined surface 63 Vertical surface 65 Cam follower 68 Connecting rod DC Power source (voltage application device)

Claims (6)

An electrostatic film forming apparatus that deposits powder onto an object by electrostatic force,
a screen disposed facing the object;
a rubbing roller for rubbing the powder into the screen;
A roller rotation mechanism that rotates the rubbing roller around its axis;
a power source that applies a voltage between the screen and the object;
A striking device having a hammer that applies intermittent strikes to the screen is provided ,
An electrostatic film forming apparatus , wherein a period of the strikes applied by the hammer to the screen is synchronized with a rotation speed of the rubbing roller . The electrostatic deposition apparatus of claim 1, wherein the impact device further includes an adjustment device configured to adjust the strength of the impact that the hammer applies to the screen. An electrostatic film forming apparatus that deposits powder onto an object by electrostatic force,
a screen disposed facing the object;
a rubbing roller for rubbing the powder into the screen;
A roller rotation mechanism that rotates the rubbing roller around its axis;
a power source that applies a voltage between the screen and the object;
A striking device having a hammer that applies intermittent strikes to the screen is provided,
The hammer is disposed so as to strike the screen in the longitudinal direction. An electrostatic film forming apparatus that deposits powder onto an object by electrostatic force,
a screen disposed facing the object;
a rubbing roller for rubbing the powder into the screen;
A roller rotation mechanism that rotates the rubbing roller around its axis;
a power source that applies a voltage between the screen and the object;
A striking device having a hammer that applies intermittent strikes to the screen is provided,
The striking device has a spring that presses the hammer against the screen. 5. The electrostatic deposition apparatus according to claim 4 , wherein the impact device has a cam follower connected to the hammer and a circular cam rotatable integrally with the rubbing roller. the striking device further comprising an adjustment device configured to adjust the strength of the strike applied by the hammer to the screen;
6. The electrostatic deposition apparatus according to claim 4 , wherein the adjustment device further comprises a support member for supporting an end of the spring, and a position adjustment mechanism for adjusting a position of the support member.

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