JPS6215257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for electrostatic powder coating of substantially axisymmetric objects, such as glass bottles or shafts, and in particular to a method and apparatus for electrostatic powder coating of substantially axially symmetrical objects such as glass bottles or shafts, particularly those held at a temperature below the melting point of synthetic resin powder. Synthetic resin powder is electrostatically applied to the surface of an axially symmetrical object, then excess powder (hereinafter referred to as surplus powder) is removed from designated areas, and then heated to coat the synthetic resin film. The present invention relates to a continuous electrostatic powder coating method and apparatus for a substantially axially symmetrical object, which is characterized in that it is formed on the surface of an object to be coated.

In recent years, it has become desirable for glass bottles for carbonated drinks such as cola and cider to be provided with a synthetic resin coating on the surface of the bottle in order to prevent damage due to an increase in internal pressure due to sunlight or other agitation. An electrostatic powder coating method is a method for forming such a synthetic resin film. However, since glass bottles are electrically insulating at room temperature, it is common practice to preheat the glass bottle to a temperature higher than the melting point of the synthetic resin powder when performing electrostatic powder coating. For example, in order to lower the electrical resistance of the glass, a glass bottle is preheated to a temperature above the melting point of the resin, and then synthetic resin powder is electrostatically coated on its surface using an appropriate method, and this is further heated and synthesized. There is a method of forming a resin film. However, in this type of method, since the glass bottle is preheated, it is almost impossible to remove the powder once it has adhered to the glass bottle. It is common to apply the powder while creating a masking gas jet. However, even if this type of method is used, it is nearly impossible to perform complete masking on a practical production line, and synthetic resin powder may adhere to the bottle mouth where the cap is placed, resulting in incomplete capping and day capping. It is unavoidable that serious problems such as foreign matter contamination due to resin coating fragments and the like cannot be avoided. In addition, there are unresolved operational technical problems such as synthetic resin powder adhering to the gripping part of the gripping device, and continuous operation being interrupted due to the accumulation of synthetic resin powder on the gripping device. be. In addition, the thickness of the upper edge of the formed resin coating is uneven and tends to become thin, and it is also formed unevenly, so the coating is likely to peel off and break when the bottle is washed or transported and handled, resulting in the longevity of the glass bottle. A fatal problem has arisen for returnable glass bottles, which is the shortening of the time. Also, in order to increase the commercial value of glass bottles, it is necessary to form the upper edge of the coating straight and clearly with an even thickness, but there is no method for applying electrostatic powder coating to preheated glass bottles. It is difficult to satisfy this requirement.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional method detailed above by providing a method in which a silent discharge electrode plate is gripped by a gripping device in an electrostatic powder coating chamber provided at the main parts of both side walls. The object to be coated is transported, the charged powder is fed into the coating chamber, a silent discharge is generated at the electrode plate, the powder is applied to the surface of the object to be coated, and then the powder is applied to the surface of the object to be coated. It is an object of the present invention to provide a continuous electrostatic powder coating method characterized in that the excess powder coated on designated parts of a kimono is removed by suction.

Another object of the present invention is to electrostatically apply synthetic resin powder onto the surface of an unpreheated object that is held at a temperature below the melting point of the synthetic resin by being gripped and carried by a gripping device. A powder coating room and a surplus powder removal device that sucks and removes excess powder from designated areas of the powder layer coated on the surface of the object to be coated in the electrostatic powder coating room. This allows the powder to form a powder layer with a uniform thickness and clear boundary layer only on designated areas on the surface of the object to be coated, and then by heating it, a synthetic resin with high durability and commercial value is created. An object of the present invention is to provide an electrostatic powder coating device that can manufacture coated objects with high productivity.

Approximately axially symmetrical objects that can be applied to the electrostatic powder coating method and apparatus of the present invention include glass bottles, various types of shafts, bowling pins, and the like. In this document, "unipolar" means that the charge of the powder is only one polarity, either positive or negative.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the method of the present invention is applied to an electrostatic powder coating apparatus for glass bottles will be described in detail below with reference to the accompanying drawings.

The illustrated electrostatic powder coating device for carrying out the method of the present invention electrostatically coats synthetic resin powder onto the surface of a glass bottle that is gripped and carried by a chuck of a movable gripping device. an electrostatic powder coating room,
This electrostatic powder coating chamber includes a surplus powder removing device that removes excess powder from the top and/or bottom of the glass bottle and other designated areas of the powder coated on the surface of the glass bottle in the electrostatic powder coating chamber.

As shown in FIG. 1, the glass bottles 1 to which synthetic resin powder is to be applied are fed one by one by a bottle supply device (not shown), and the chucks of a chain conveyor-type gripping device 2 are fed. 3 grabs the head of the bottle 1, suspends it, and transports it to the entrance of the coating chamber 5. The coating chamber 5 consists of an elongated casing 6 having a cross-sectional shape as shown, and has an outlet at the other end, and the bottle 1 suspended and supported by the gripping device 2 moves within the coating chamber 5. It looks like powder is applied as it passes through. Therefore, the top surface of the casing 6 is opened in the form of a slit to allow movement of the chuck 3 of the gripping device 2. A suction section 7 is provided on both sides of the upper part of the casing 6 of this coating chamber 5, a silent discharge electrode plate 8 is provided on both sides of the casing 6, and a powder is pre-charged at the bottom to fill the inside of the casing 6. A feeding section 9 is provided for feeding the material into the container. The feeding portions 9 are preferably provided at appropriate intervals depending on the length of the casing 6.

The feeding section 9 processes the synthetic resin powder, which is a raw material supplied to the pre-charging section 11, by corona discharge, contact charging,
The casing 6 may be precharged by other suitable methods and then introduced into the casing 6 by inlet air. The introduced powder is electrostatically applied to the bottle 1 passing through the casing 6 by the action of the electric field from the silent discharge electrode plate 8 toward the bottle 1 in the casing 6, and the surface of the bottle 1 is well charged. A layer of dense powder is formed. The current or voltage of the silent discharge electrode plate 8 and the precharging section 11 is controlled by a suitable electric control device 12. This silent discharge electrode plate 8
For example, as shown in Japanese Unexamined Patent Publication No. 51-8347, a silent discharge is generated on the plate surface by applying an alternating current voltage between parallel wire electrodes installed in an insulating plate, and In addition to preventing the adhesion of resin powder, the DC voltage superimposed thereon generates an electric field and a minute discharge current from the plate toward the bottle, which is the object to be coated.

The suction section 7 provided in the upper part of the coating chamber 5 has a suction chamber 15 formed on both sides of the upper part of the casing 6, a suction port 16 provided on the inner surface side, and an outlet port 17 provided on the outer surface side. The outlet 17 is connected to the suction pipe 1.
8 to a suitable dust collector and suction fan (not shown). Therefore, the suction part 7
is used to prevent powder from leaking out of the casing 6 through the slit-like opening, and to collect powder that has not been applied to the bottle for reuse.

In addition, a feeding section similar to the feeding section 9 is provided on the side of the casing 6 to further feed the pre-charged powder from the side to a specific part of the bottle of the object to be coated. This additional inlet also has a built-in pre-charging section and can be used when particularly thick powder layers are required or when the shape of the glass bottle requires compensation of the powder layer thickness. The operation and effect are the same as those of the pre-charging section 11 of the feeding section 9 described above.

A surplus powder removing device 21 is provided next to the coating chamber 5, and the excess powder is removed from the powder coated on the surface of the bottle 1 in the coating chamber 5 at a desired location such as the top or bottom of the bottle. is removed. This surplus powder removing device 21 is provided close to the top or bottom of the bottle 1 as shown in FIGS. The suction slits 22 and 23 are connected to a suitable dust collector and suction fan, and can suck and remove a desired portion of powder. When a bottle coated with powder comes to the surplus powder removing device 21, the chuck 3 of the gripping device 2 is rotated by an appropriate means to remove the bottle 1.
Powder can be removed from the required part of the head or bottom of the machine.

In addition, as shown in FIGS. 6 and 7, upper and lower suction slits 22' and 2 of the surplus powder removing device 21'
The suction ports 3' are partitioned by appropriate partition walls 24 and 25, and a flow rate restriction device 26 is installed for each suction port as necessary.
31, the suction effect can be further improved by setting the suction air volume according to the part and shape. In particular, it is preferable that the tip portions of the partition walls 24, 25 slightly protrude from the suction port surface and serve as spacers to maintain an appropriate gap between the gripping device and the bottom and mouth of the chuck bottle.

For example, in FIG.
is set to a relatively high value, whereas the suction speed 34, which aims to form a clear boundary 35 at the upper end of the powder layer, is set to a relatively high value depending on the amount of charge and the degree of compaction of the powder layer. , 33, it is often better to set it to a relatively low value. This relationship is based on the suction speed 3 for the purpose of forming the boundary 36 in FIG.
7 and 39, and the suction speed 38, which is aimed at completely removing the central portion, is also substantially the same. The surplus powder removal method in this invention includes the mouth part,
Of course, it can be applied to areas other than the bottom.

As described above, according to the electrostatic powder coating method and apparatus of the present invention, when powder is coated onto a glass bottle, the powder is coated to a uniform thickness on the surface of the glass bottle in the electrostatic powder coating chamber. Then, the powder is electrostatically applied in a well-charged and well-organized state, and then the excess powder in the required area to be removed is removed using a surplus powder removal device so that sufficient and clear boundaries are formed. Since it is removed, a uniformly thick synthetic resin coating is formed by post-heating, which makes it possible to extend the life of the bottle and at the same time increase the commercial value of the bottle. Furthermore, according to the present invention, the gripping device can completely remove the excess powder, which makes long-term continuous operation possible.
It is characterized by extremely high productivity.

In the above, the present invention has been explained in the case where it is applied to the application of synthetic resin powder to a glass bottle, but it is also possible to apply the powder to the required part of an approximately axially symmetrical object such as a shaft or a bowling pin. It will be readily appreciated that it can be used to perform electrostatic deposition. It goes without saying that the present invention can be applied not only to the application of synthetic resin powder but also to the application of electrostatic powder such as frit powder for enamel or other inorganic powders.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an electrostatic powder coating chamber of a bottle powder coating apparatus for carrying out the method of the present invention;
Figures 2 and 3 are schematic sectional views of the upper and lower suction slits of the surplus powder removal device, Figures 4 and 5 are top and bottom views, and Figures 6 and 7 are modifications of the surplus powder removal device. This is a diagram similar to FIGS. 2 and 3. In the figure, 1... bottle, 2... gripping device, 5... coating chamber, 6... casing, 7... suction part, 8...
Discharge electrode plate, 9... feeding section, 21, 21'... surplus powder removal device.

Claims (1)

[Scope of Claims] 1. A silent discharge electrode plate is provided in an electrostatic powder coating chamber provided on the main parts of both side walls to convey the object to be coated, which is gripped by a conveying and gripping device, into the electrostatic powder coating chamber. An electric field and a minute discharge current are formed toward the object to be coated by the silent discharge electrode plate, and the powder precharged to a unipolar state is coated with the electrostatic powder under the electric field and minute discharge current. A continuous electrostatic powder coating method characterized by feeding powder into a room and electrostatically coating the surface of an object to be coated. 2. The continuous electrostatic powder coating method according to claim 1, characterized in that the surface temperature of the object to be coated is maintained at a temperature below the melting point of the powder to be coated. 3. An electrostatic powder coating chamber in which silent discharge electrode plates that form an electric field and a minute discharge current toward the object to be coated are provided on the main parts of both side walls, and a conveying and gripping device that grips and conveys the object to be coated; 1. A continuous electrostatic powder coating device comprising means for feeding unipolar pre-charged powder between an object to be coated and the electrode plate. 4 The electrostatic powder coating chamber consists of an elongated casing through which the object to be coated enters and exits, a silent discharge electrode plate provided across the main parts of both side walls of the casing, a suction section provided at the top of the casing, and a casing. 4. The continuous electrostatic powder coating apparatus according to claim 3, further comprising a precharge feeding section for feeding unipolar precharged powder from the bottom or the side or both.