JPH0143584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for spray painting the inner surface of a two-piece can with a water-based paint after can manufacturing.

Conventionally used can paints include oleoresinous paints, phenol formaldehyde paints, wax-type paints, and vinyl paints, but most of them are flammable, and ethyl-based paints are used as solvents for these paints. Ether and ethylene glycol are both highly emissive, and when mixed with air in a certain proportion, solvent gases not only pose a risk of explosion, but are also harmful to the human body, deteriorating the work environment, and reducing work efficiency. In order to improve ventilation, large-scale ventilation equipment is required, which is a major cause of high product costs.

In addition, attempts have been made to use non-volatile water-soluble solvents as paint solvents, but since the solvents do not have wicking properties, it takes a relatively long time for the water-based paints to dry after painting. Moreover, if a thick coating is applied and then baked, the solvent may evaporate at once, causing foaming and creating a caramel-like appearance.

However, if the coating layer is thin, a problem arises in corrosion resistance. In particular, for two-piece tin cans, it is desirable to apply the coating in two coats to improve corrosion resistance, but in order to improve the uniformity of the coating, the base coat is applied underneath and the top coat is coated on top. It must be ensured that the coatings do not mix with each other. For this reason, it is desirable to cause the coating film to lose its fluidity after the base coating, but in order to save energy, it is desirable to perform baking only once after two coatings have been completed.

On the other hand, if a flange coated with paint that dries relatively slowly comes into contact with a guide for position regulation during transportation, not only will the undried paint peel off, but
This dries into small pieces and adheres to other parts of the painted surface, creating so-called flange gobs.

In order to solve the above-mentioned technical problems, this invention provides the following coating method and apparatus, namely, the first step of painting the inner surface of the can with a spray machine, and the preliminary coating of the can body and can bottom simultaneously with a high-frequency induction heating coil. The second step is drying, the third step is to naturally cool the pre-dried cans to room temperature on a storage conveyor, the fourth step is to paint the inside of the can with a spray machine, and the painted inside of the can is baked in a baking oven. A method for painting the inner surface of a two-piece can consisting of a fifth step,
A can feeding device that feeds the cans transported from the previous process to the spray machine, a can holding device that rotates the cans fed from the can feeding device, a sprayer that sprays the inside of the can, and painting at a predetermined position. A base spray machine consists of a guide for guiding the can bodies and can bottom drying equipment, a belt for conveying the cans, and a belt for pre-drying the can bodies and seaming ends. A can body/bottom drying device consisting of several high-frequency induction heating coils, a storage conveyor for naturally cooling the pre-dried cans, and a can for supplying the cans transported from the storage conveyor to the spray machine. A feeding device, a can holding device that rotates while rotating the cans fed from the can feeding device, a sprayer that sprays the inside of the can, and a guide guide that guides the cans that have been repainted at a predetermined position to the next baking furnace. The present invention provides a two-piece can inner surface coating apparatus that is equipped with a top spray machine consisting of a top spray machine and a baking furnace for baking the painted inner surface of the can.

Next, the method of the present invention will be explained in detail based on the drawings.

Two-piece can with flange made in the previous process 1
is conveyed to the can supply device 2 by an appropriate method, 2
Piece cans 1 are fed to a base spray machine 4 by a screw conveyor 3. The base spray machine 4 includes a can holding device 6 which rotates about a shaft 5 by an appropriate drive device and rotates the two-piece can at a constant speed, and a can holder device 6 which is slidable in the axial direction within the two-piece can 1. Since a suitable spray 7 such as a movable spray is disposed, the two-piece can 1 is held in a continuous rotation state by the can holding device 7, rotated around the shaft 5, and simultaneously rotated. Inside, the inner surface of the two-piece can 1 is continuously coated with water-based paint by a sprayer 7. When the coating is completed, the flanged two-piece can 1 is guided by the guide 8 to the first flange drying device 9, and the two conveyor belts 1 disposed in the first flange drying device 9
0 and 10, the can body is rotated and conveyed at a constant speed to the can body/end drying device 11 for the next step.

In the first flange drying device 9, a high frequency induction heating coil 12 is installed at a position where the paint on the flange of the two-piece can 1 is dried.
The paint on the flange of the piece can 1 is heated to 80 to 150°C and pre-dried. The two-piece can 1, on which the paint on the flange part has been pre-dried, is transported to the can body/bottom drying device 11 for the next process, and then conveyed by a conveyor belt 13 disposed in the can body/can bottom drying device 11. It is transported to the storage conveyor 14. The can body/can bottom drying device 11 is equipped with high-frequency induction heating coils 15 and 16 at positions for pre-drying the paint on the can body and can bottom of the two-piece can 1. The paint on the can body and can bottom is 80 to 150℃.
It is heated and pre-dried. Further, since the high-frequency heating coil 16 for the can body is installed at an angle as shown in FIG. 2, the entire can body can be uniformly heated and dried. The two-piece cans with dried can bodies and ends transported to the storage conveyor 14 are conveyed to the can supply device 17 while being naturally cooled on the storage conveyor 14, and are then top sprayed by the screw conveyor 18 of the can supply device 17. machine 19
supplied to The top spray machine 19 has a can holding device 21 which rotates around a shaft 20 by an appropriate drive device and rotates the two-piece can at a constant speed, and a can holder 21 which is also slidable in the axial direction inside the two-piece can 1. Since a suitable spray 22 such as a movable sprayer is provided, the two-piece can is held in a continuous rotation state by the can holding device 21 and rotated around the shaft 20, and during this rotation, the two-piece can 1 The inner surface is again successively coated with water-based paint by means of a movable sprayer 22.

When the second coating is completed, the two-piece can 1 is moved to the second flange drying device 24 by the guide 23.
The can body is held between two conveyor belts 25, 25 disposed in the second flange drying device 24, and is conveyed to the baking furnace 27 via the next appropriate conveyor 26 while rotating. In the second flange drying device 24, a high-frequency induction heating coil 28 is installed at a position where the paint on the flange of the two-piece can 1 is dried, so that the paint on the flange of the two-piece can 1 is heated up to 80% during transportation. It is heated to 150°C and pre-dried again. The two-piece can 1, whose flange paint has been pre-dried again, is transferred to a baking oven 27 on a conveyor 26.
The inner surface of the flanged two-piece can 1 is completely baked in the baking furnace 27.

Furthermore, a two-piece can without a flange can be painted in exactly the same process as described above, by omitting the step of drying the flange paint using the first and second flange dryers 9, 25.

The present invention achieves the following unique effects with the above configuration.

(b) By pre-drying the flange paint with a high-frequency induction heating coil at the outlet of the spray machine, the occurrence of flange gobs is prevented.

(b) Since a can body and can bottom drying device is installed, the entire can can be pre-dried at once, which is not only efficient but also
The installation space is also small.

(c) Since the high-frequency induction heating coil for the can body is installed at an angle, the can body can be heated evenly.

(d) Base spray machine, first flange device,
A can body/can bottom drying device, a storage conveyor, a top spray machine, and a baking furnace are arranged in succession, and the process is as follows: continuous spray → flange predrying → can body/
Since the process includes drying the can bottom → natural cooling → spraying and baking, the inner surface of a two-piece can with flanges can be coated uniformly and continuously in large quantities using water-based paint. Therefore, cost reduction can be expected. In addition, 2
In the case of piece cans, similar effects can be obtained except for the flange process.

(e) Since water-based paint can be used, it is safe without any risk of explosion, and the work environment can be improved as no harmful gases are emitted.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of the device used in the method of the present invention, and Fig. 2 is a schematic explanatory diagram of the can body/end drying device. : Screw conveyor, 4: Base spray machine, 5: Axis, 6: Can holding device, 7: Movable spray, 8: Guidance guide, 9: First flange device, 10: Conveyor belt, 11: Can body/can bottom Drying device, 12: High frequency induction heating coil, 13: Conveyor belt, 14: Storage conveyor, 1
5, 16: High frequency induction heating coil, 17: Can feeding device, 18: Screw conveyor, 19: Top spray machine, 20: Shaft, 21: Can holding device,
22: Movable spray, 23: Guidance guide, 24:
Second flange drying device, 25: conveyor belt,
26: conveyor, 27: baking furnace, 28: high frequency induction heating coil.

Claims (1)

[Claims] 1. A method for painting the inner surface of a two-piece can, comprising the following steps: (b) The first step is to paint the inner surface of the can with a spray machine. (b) The second step is to pre-dry the can body and can bottom simultaneously using a high-frequency induction heating coil. (c) The pre-dried cans are placed on a storage conveyor. (d) the fourth step is to paint the inside of the can with a spray machine; (e) the fifth step is to bake the painted inside of the can in a baking oven. 2. A method for painting the inner surface of a two-piece can, which consists of the following steps: (b) The first step is to paint the inner surface of the can with a spray machine. (b) The second step is to pre-dry the flange paint using a high-frequency induction heating coil. (c) The can body and bottom are simultaneously coated with a high-frequency induction heating coil. 3rd step of pre-drying, (d) 4th step of naturally cooling the pre-dried cans to room temperature on a storage conveyor, (e) 5th step of painting the inner surface of the can with a spray machine, (f) flange The sixth step is to pre-dry the paint using a high-frequency induction heating coil; (g) the seventh step is to bake the painted inner surface of the can in a baking oven. 3. A can feeding device for feeding the two-piece cans transported from the previous process to the spray machine, a can holding device that rotates the cans fed from the can feeding device, and a can holding device that moves in the axial direction inside the can. A base spray machine consists of a movable sprayer that sprays cans, a guide that guides the cans coated in a predetermined position to the next can body/can bottom drying device, and a conveyor belt and can body that transport the cans. and a can body/can bottom drying device consisting of two high-frequency induction heating coils for pre-drying the can bottoms, a storage conveyor for naturally cooling the pre-dried cans, and A can feeding device for feeding cans to a spray machine, a can holding device that rotates the cans fed from the can feeding device, a movable sprayer that moves in the axial direction inside the can and sprays, and A two-piece product characterized by a top spray machine consisting of a guide for guiding repainted cans to the next baking oven, and a baking oven for baking the inner surface of the painted cans. Equipment for painting the inside of cans.