JPS6358629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for electrostatically applying synthetic resin powder or the like in the form of spots or narrow strips.

The purpose of this invention is to electrostatically apply synthetic resin powder, etc., at high speed and efficiently in the form of thin strips or spots with clear boundaries using an extremely simple and small device, and then heat this to form the required protective layer. An object of the present invention is to provide an electrostatic coating device for forming a .

1, 2, and 3 are diagrams showing a first embodiment of an electrostatic powder coating apparatus for carrying out the present invention, and FIG. 3 is a cross-sectional view taken along the - line in FIG. 1, and FIG. 3 is a diagram showing the structure as seen from the direction along the - line in FIG. In the following description, the components shown in FIGS. 1, 2, and 3 may be collectively referred to as the first embodiment. In the first embodiment, the electrostatic powder coating apparatus according to the present invention has a main body 1 made of an insulating material, which is installed in close proximity to a grounded workpiece 15 with an extremely small gap 14 in between. A closed space is described above, and a powder feeding device 3 is directed toward this closed space 2.
As shown by an arrow 4 through the closed space 2, insulating particles such as synthetic resin powder suspended in gas are usually fed into the closed space 2. Particles such as synthetic resin powder fed in this way are fed into the closed space 2 which has a much larger cross-sectional area than the feeding device 3, so the traveling speed within the closed space 2 is is reduced to a fraction or several tenths of the traveling speed inside the feeding device 3. On the other hand, closed space 2
has a means for evacuating the closed space, and is configured to evacuate a larger amount of gas, as shown by arrow 9, than the amount of gas normally shown by arrow 4. .

On the other hand, on the upper part of the synthetic resin powder feeding device 3, there is a corona discharge electrode 5 whose tip is connected to a high voltage applied by a high voltage power source (not shown) through a lead wire 5a. It is installed so as to be located inside the closed space 2. This corona discharge electrode performs appropriate corona discharge toward the grounded workpiece 15, and the workpiece 15 visible from inside the closed space 2 from the tip of the corona discharge electrode. A corona discharge current is caused to flow toward the slit-shaped portion of the coating material 15, and an electrostatic field directed toward the object 15 to be coated is formed. Note that the arrow 7 indicates that a sheath 6 surrounds the tip of the corona discharge electrode 5 to prevent particles from fusing to the tip of the corona discharge electrode 5 and preventing smooth corona discharge. Air is supplied as shown by arrow 7 to blow out the gas at high speed. Also, the gas inlet port 10 attached to the main body 1
is a gas inlet port for introducing the gas indicated by the arrow 11 toward the closed space 2; It is a means for inhaling. In the powder electrostatic coating device according to the present invention formed as described above, the closed space 2 is
The synthetic resin powder introduced into the closed space 2 moves toward the exhaust pipe 8 at a relatively slow speed, but during this time, it is affected by the corona discharge current flowing from the tip of the corona discharge electrode 5 toward the object to be coated. As a result, the object is electrically charged, and the third electrode
A to-be-coated object 15 is grounded through a charged powder outlet, that is, a slit 17, so as to face and communicate with the to-be-coated object on the surface of the applicator main body 1 shown in the figure, which is close to the to-be-coated object.
A powder layer 16 is gradually electrostatically applied to the surface of the powder. At this time, since the mixed airflow of gas and synthetic resin powder flows along the surface of the object to be coated, the airflow does not collide with the surface to be coated.

Therefore, the synthetic resin powder is not scattered along the surface to be coated due to dynamic pressure, so that it can be reliably and uniformly adhered to the surface to be coated.

The remaining powder thus coated on the object to be coated is discharged out of the system through the exhaust pipe 8, recovered by a recovery device, and reused.
In this case, an amount of gas larger than the amount of gas blown into the closed space 2 by the powder feeding device 3 is transferred to the exhaust pipe 8.
Therefore, at the gap 14 formed between the powder coating device main body 1 and the object to be coated, the powder coating device main body 1 approaches the object to be coated toward the closed space 2. Since external gas is sucked in from the edge of the closed space 2, the synthetic resin powder etc. present in the closed space 2 will not be scattered over a wider area than the width of the slit 17 shown in Fig. 3. , when the object 15 to be coated moves from right to left in FIG. 1, the slit 1 in FIGS.
It is possible to form an electrostatic powder coating layer 16 with a width slightly narrower than that of 7 with extremely clear boundaries, and this is an electrostatic powder coating layer 16 for electrostatically protecting seams, welded areas, etc. of cans. It is extremely effective when applied as a device, etc.
In this case, in order to adjust the speed of the gas sucked through the gap 14, a gas flow rate adjustment device (not shown in the figure) is attached to the gas inlet 10, and the amount of gas sucked through the gas inlet 10 is adjusted. A suitable result may be obtained by adjusting the . Further, as is clear from FIG. 2, the coated powder is prevented from spewing out from the gap 14 between the object 15 and the coating device main body 1. In order to perform electrostatic powder coating with clear boundaries between layers 16 and higher commercial value, it is necessary to
Another slit 19 is provided between the slit 17 facing 5 and the outside, and this is connected to the conduit 18,
Furthermore, this is connected to the tube 12 in FIG. 1, and a minute amount of air is blown out or discharged from this slit 19 to further clarify the boundary of the coated powder layer 16 and scatter it. It is possible to reduce the amount of synthetic resin powder and perform effective electrostatic powder coating. In that case, whether air is taken in or exhausted from the pipe 12 depends on the advancing speed of the object to be coated, the thickness of the powder coating layer, and the gap 14 between the powder coating apparatus main body 1 and the object to be coated 15. It may be selected appropriately depending on the distance to be obtained, etc. The most significant feature of this method is that, compared to conventionally known belt-shaped electrostatic powder coating devices, the closed space 2 where the powder exists is formed by the main body 1 made of an insulating material. The formed and floating powder is confined in this limited space, and the synthetic resin powder, etc. is ejected in a direction almost parallel to the object to be coated, and the powder is ejected through an exhaust pipe 8 in a direction away from the object to be coated. is provided, thereby suctioning the remaining powder, thereby preventing the powder from leaking to the outside from this closed space 2 even if powder is continued to be supplied into this space when there is no object to be coated. Coating is performed by a strong electric field formed between the corona discharge electrode 5 and the object to be coated only when the object to be coated 15 is present, and the object to be coated disappears. In some cases, a very important feature is that powder leakage to the outside is automatically stopped. can be carried out. Furthermore, according to this method, this device is not only applicable to thin strip-shaped electrostatic powder coating, but also allows the object to be coated to approach this closed space in a perpendicular direction, and after coating is completed, Spot-like electrostatic powder coating can also be carried out by removing the slit 17 in the right angle direction, and in this case, by forming the slit 17 into a desired shape such as a circle, this purpose can be achieved. In this method, an example has been described in which a corona discharge electrode protruding into the closed space 2 is applied as a method of charging the powder sent into the closed space 2, but the means for this purpose is not necessarily limited to this. Instead, it is also possible to achieve the objective by charging the object to be coated in advance outside the coating head 1 and providing means for forming an electric field inside the closed space 2. Yes, this is also within the scope of the present invention. Good results may also be obtained by using these methods in combination.

FIGS. 4 and 5 show another embodiment in which the electrostatic powder coating apparatus according to the present invention is applied to seal a welded joint on the inner surface of a can.
Note that FIG. 5 is a cross-sectional view taken along the - line in FIG. 4, and in the following description, the components shown in FIGS. 4 and 5 may be collectively referred to as the second embodiment.

In the second embodiment, when forming an electrostatic powder coating layer on a joint, the housings 15a, 15b, 15c are kept at a predetermined interval by a conveyor 27 at a constant speed in the direction of an arrow 29. and transported. The electrostatic powder coating head 1 according to the second embodiment of the present invention has the same structure in principle as that shown in the first embodiment, and is set so that the slit 17 is located above. A support device 26 is provided to define a support device 26, which passes through the powder supply pipe 4 shown by an arrow 4, an arrow 9 showing an exhaust gas from the closed space 2, and an electric field and a corona inside the closed space. A conductive wire 5a is provided for forming a discharge, and the support device 26 is grounded as required. This second
In the embodiment, the belt 32 is provided to prevent the synthetic resin powder from being slightly ejected and adhering to the outside of the housing when the gap between the housings passes through the main body 1 of the applicator. This is carried out by pulleys 30 and 31 in synchronization with the transport speed of the casing.
Masking is carried out by pulleys 34 and 35 so as to be driven by the electrostatic powder coating head and in close contact with the outside of the housing as shown in FIG. Note that 33 is a belt cleaner for removing minute amounts of synthetic resin powder adhering to such a masking belt. In this case, it is only necessary to place the belt in close contact with the outside of the case as shown in Fig. 5 and remove the synthetic resin powder adhering to the belt in the space between the cases. It is not necessary to apply the belt on the perforated plate with cutouts on the same side as the powder application head, as in No. 47-34385.

FIGS. 6 and 7 show still another embodiment of the band-shaped electrostatic powder coating device according to the present invention, and FIG. 7 shows -
It is a line part plan view showing the shape of the surface of the powder removing device 21 that faces the main body 1 of the coating device. The objects to be coated are at a certain interval 2 like 15a and 15c.
In the case where the powder is supplied from right to left while maintaining zero, the method shown in the second embodiment can be used to prevent the powder from wrapping around and adhering to the back surface of the object that does not need to be coated. However, the embodiments shown in FIGS. 6 and 7 (hereinafter may be collectively referred to as the third embodiment) describe other methods that should be applied in such cases. It is something. In the third embodiment, the powder coating apparatus main body 1 is the same as that shown in the first embodiment, but there is one object to be coated and one object to be coated on the opposite side of the object to be coated. FIG. 6 shows a detailed structure of a powder removing device 21 for suctioning and removing a small amount of synthetic resin powder leaking through the gap 20 between the two. This powder removal device 2
1 includes a coating slit 1 of the powder coating device main body 1.
A series of longitudinally divided inlets are provided opposite 7, each inlet leading to the duct 22 through a flow-limiting restriction 24, thereby allowing exhaust or supply air as indicated by arrow 23. is now being carried out.

In the present invention, since no electric field is formed in the gap 20 between the objects to be coated and the objects to be coated, the floating powder supplied by the powder feeding device 3 and existing in the closed space 2 Powder is applied to objects 15d to 1
5e's electrostatic powder applicator body 1, and it almost never sticks to the side opposite to the main body 1 of the electrostatic powder applicator 5e. In order to prevent such a small amount of synthetic resin powder from leaking out, a small amount of air is introduced into the closed space through this divided intake port, as shown by arrow 23. The leakage of this very small amount of powder can be prevented by blowing slightly towards the direction, and conversely, a small amount of gas can be discharged through a series of intake ports 25 as shown by the arrow 23 to prevent leakage. By discharging a small amount of resin powder out of the system, it is possible to effectively prevent the powder from being applied to unnecessary parts of the object to be coated. In this case, 36
The communication port indicated by is a communication port for discharging excess air out of the system when there is an object to be coated. Depending on the size of the gap between the two, providing this communication port may be effective in preventing the powder from being applied to unnecessary parts of the object to be coated.

8 and 9 describe the fourth embodiment of the present invention, and in FIG. conveyor 27 at a certain interval.
A belt driven by pulleys 30 and 31 is interposed between the coating device body 1 and the housings 15a, 15b, 15c, which are the objects to be coated, which are transported by the There is. As shown in Fig. 8, this belt is a perforated belt with holes 37 spaced apart at regular intervals so that only the part of the case required to be coated with powder can be left and the other parts can be masked. The objects to be coated 15a, 15b,
Only the portion of the powder coating device 15c that needs to be coated faces the powder coating device 1, and the other portions are hidden from the powder coating device main body 1. Therefore, the powder that slightly leaks from the slit facing the object to be coated in the powder coating device main body 1 is coated on the powder and continuously discharged, and the belt is constantly cleaned by the excess powder removal device 33. This completely prevents leaked powder from being applied to unnecessary parts and allows continuous and safe operation.

In this case, the belt 36a may be made of metal or conductive material when the case to be coated is at room temperature, but when the temperature is high, the belt 36a may be made of a non-adhesive material such as Teflon or the like. It is necessary to select a material that allows the device to operate effectively and continuously.

Since the present invention is constructed as described above, outside air is sucked into the closed space between the edge and the object to be coated from the edge closer to the object to be coated. The synthetic resin powder, etc. present inside will not be scattered over a wider area than the width of the opening (slit), and the airflow from the slits provided at the edge will prevent it from spreading to the surface to be coated directly below the edge. Smearing is completely prevented.

Therefore, a fine band-like or spot-like powder layer with very clear boundaries can be obtained.

Furthermore, since the powder is supplied into the closed space along the surface of the object to be coated, the powder does not collide with the surface to be coated.

Therefore, the synthetic resin powder and the like are not scattered along the surface to be coated due to dynamic pressure, so that the powder can be reliably and uniformly attached to the surface to be coated.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention; FIG. 1 is a longitudinal sectional view thereof, FIG. 2 is a sectional view taken along the line - in FIG. 1, and FIG. 3 is a bottom view taken along the line - in FIG. Fourth
The figure is a longitudinal sectional view of the second embodiment, FIG. 5 is a sectional view taken along the line - in FIG. 4, FIG. 6 is a longitudinal sectional view of the third embodiment, and FIG. Plan view, No. 8
The figure is a side view of the fourth embodiment, and FIG. 9 is a plan view of a portion of FIG. 8. 2...Closed space, 19...Slit.

Claims (1)

[Claims] 1. A closed space surrounded by a main body that forms a slit at the edge of the outlet for the charged powder, means for feeding the powder into the space in parallel along a plane including the outlet, and exhaust from the space. means for charging powder present in the space; means for creating an electrostatic field in the space toward the object to be coated facing the space; and means for introducing gas into the space. A powder electrostatic coating device comprising: