JPS5921244B2 - Manufacturing method for coated cans - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a coated can.

Technological means are known for producing cans by preparing a sheet metal, lubricating this sheet metal, cutting out a disc, and drawing this disc into a cup shape by means of a drawing repress.
In this case the cup is placed on the punch of a wall ironing press and forced through a series of annular dies such that the cup wall progressively decreases in thickness and correspondingly increases in height to create the desired gun. ing.

Typically, such ironing presses are lubricated by a water and oil emulsion, well known in the art, which is pumped from a sump and into the tool enclosure.

The emulsion liquid acts as both a lubricant and a coolant. After the cans are shaped, they are finished to the exact length. The lubricating oil residue is then washed away and the can is dried for internal and external coating and external decoration. The use and subsequent removal of lubricants in such processes accounts for a significant portion of the cost of the can.

The applicant has discovered the following surprising fact. The lubricant and coolant action of at least the last of the pressing steps can be achieved by the material forming part or all of the finished can cladding. That is, a coating material with a reduced water content is applied to the workpiece at least during ironing, and this coating material acts as a lubricant and cooling agent during ironing, and then acts with the hardening coating material. . Hereinafter, embodiments of the present invention will be described by way of example with reference to the accompanying drawings.

Referring to FIG. 1, in one method according to the present invention, a combined coating and lubricating material are prepared and applied to a sheet metal workpiece in a press and an article is formed from the sheet metal workpiece.

The product is then removed from the press, baked to harden the coating, and then finished if necessary. The lower part of the diagram shown in FIG.
After rinsing with coating material to smooth the surface or rinsing with water to remove some of the coating, the product is dried, finished, and sent for further processing. The press device 1 shown in FIG. 2 has a punching rod 2, a material holder 3, and a die 4, and draws the workpiece again into a pot shape 5 to form a can 6.

The tip 5 formed from sheet metal by the aforementioned drawing process is placed on a line connecting the punching rod and the die in order to be positioned above the punching rod before being punched through the die. The symbol A designates a spraying device for coating material with reduced water content, the spray emerging from this device being directed into the tip and onto the circumferential surface and onto the die, depositing a wet coating on the tip as it exits the die. In addition to forming, it also acts as a lubricant and coolant for redrawing.

The final applicator of the coating material, designated A', is a ring-shaped spray device, which serves to smooth the coating onto the cans exiting the die 4. This last applicator is also a re-shaped tip or irrigation die 4
It may be in the form of a circular brush that surrounds it as it exits. If desired, the coating material applied by the final applicator may supplement the material already coating the can as it exits the die. The frictional force between the tip 5 and the die 4 ensures that the can is warm when it leaves the press 1, and this warmth
It contributes to the curing effect of the coating, which is generally insufficient. Examples of coating materials with reduced water content include ethyl
It is made by adding acrylate/styrene/acrylic acid copolymer to acrylic resin.

Excess coating material is collected in a collection pan 12 from which it flows into a material sump 15. Filter 14 filters through the water-thinning coating and recirculates it by pump 13. Once the cans 6 leave the die 4, they are picked up by a magnetic or vacuum conveyor 7 and conveyed by a second conveyor 8 through a drying oven 9, where they are heated by radiant elements (not shown) to coat them. harden.

The conveyor 7 receives the cans 6 in a wet state, such that when the conveyor is at room temperature, droplets falling from the cans 6 do not interfere with the conveying action of the conveyor. That is, since the coating material is a solution with low viscosity, the conveyor 7
When being transferred upward while placed horizontally, the can 6
The droplets remaining on the outer circumferential surface will fall due to the action of gravity. The cans 6A that have passed through the conveyor 7 arrive at the second conveyor 8 and are conveyed through the drying oven 9, but the droplets have fallen from the cans and do not seriously contaminate the second conveyor. The resin is cured by exposure to hot gas or other known devices. When the coating has hardened to at least a handleable condition, cans 6B are conveyed by conveyor 10 to finisher 11.

This finishing step cuts out the burrs created during the drawing process and ensures that all cans are at the required height. FIG. 3 shows an apparatus for carrying out an alternative method to that shown in FIG. 1, in which a workpiece in the form of a pot 30 is coated simultaneously with a press to produce a can 31. In FIG.

After subsequent partial cleaning, the coating is cured by storage. As shown in Figure 3, the press device 3 has a long stroke.
3 includes a punching rod 34, a material holder 35 that can reciprocate with respect to the redrawing die 16, a first ironing ring 17, a second ironing ring 18, a stripper 19, and a bottom forming block. and have.

The press has a reservoir 20 containing a coating material with reduced water content and a device for distributing this coating material to the processing equipment. In FIG. 3, the apparatus for distributing the coating material includes a filter 21, a pump 22 and tubing to deliver the coating material to the processing equipment. Filter 21
The pump 22 is preferably placed below the liquid level in the reservoir to reduce foaming. The tip 30 has been drawn from sheet metal in a previous step and is sent to a press 33 where a punching rod 34 and a blank holder 35 enter the tip 30 while the blank holder 35 re-shapes the bottom of the tip. The punching rod 34 is held against the front surface of the drawing die 16, and the punching rod 34 continues its axial movement to re-draw the tip with the drawing die 16.
The tip is punched through, reducing the diameter but leaving the wall thickness essentially unchanged.

The punching rod 34 continues its forward axial movement to move the redrawn tip through the first and second ironing rings 17, 18, where the cylinder of the redrawn tip is removed. Since the walls are made thinner, the side walls of the coop will be increased in length. In the apparatus of FIG. 3, the coating material with reduced water content in the reservoir is first drawn by a pump 22 through a filter 21 and through a nozzle 24 into a spout receiving space in front of a redrawing die 16. Continuously feeding, the coating material is applied to the punching rod 34, the blank holder 35 and the tip 30.

The coating material also covers each of the spacing blocks 25A, 25B,
Continuously pumped to 25C.

Each spacing block is a hollow cylinder of a length chosen to space the die 16, the rings 17, 18} and the stripper 19, respectively. Circumferential grooves cut into the outer circumferential wall of each spacing block, such as those shown at 23 in spacing piece 25B, distribute the coating material around the circumference of the block, and radial holes distribute the material into the interior hollow space. into ring 1
6, 17 and 18 on the outer surface of the tip between the passages through the dice. Spacing block 25A separates redrawing die 16 from first ironing ring 17.
The spacing piece 25B separates the first ironing ring from the second ironing ring 18. The spacing piece 25C is the second
The ironing ring 18 is separated from the stripper 19. The coating material is directed into the passage of the punching rod 34,
It is delivered from nozzle 24 and spacing blocks 25A, 25B, 25C in the form of a low velocity stream or spray. Third
A further coating applicator 26 is shown after the stripper 19 in the figure. Its purpose is to smooth the coating of the gun as it emerges from the stripper. This applicator 26 may be in the form of an annular jet or a circular brush. At the end of the stroke of the punching rod, the bottom of the can 31 presses against the bottom forming block 20.

After the bottom has been formed, the punching rod 34 is retracted and the can is removed from the punching rod 34 by the stripper 19 and retained on the bottom forming block 20. The bottom forming block 20 is one of four similar blocks carried by a rotating mandrel 40.

After the can is freed from the punching rod 34, this mandrel is rotated clockwise in the illustration to remove the can from the press and invert it before placing it on the wet conveyor 28. . Since the excess coating material adhering to the outer surface of the can 31 held on the bottom forming block 20 of the rotary mandrel 40 is a low viscosity solution, it is dripped from the outer surface of the can by the action of the rotational force of the mandrel 40 and gravity. That will happen. The conveyor 28 has a net-like belt, and this belt carries a can 31.
is passed over the washing fountain 29, which generates a wave of water of regulated height that engages the rim of the can 31A to remove drops or streams of coating material from the rim, after which the can is dried. Therefore, it is transferred to a dry conveyor 32. The spot cleaning described above prevents undue contamination of subsequent machinery, such as printing machines or finishing machines used to finish the edges of cans.
If desired, brace 1 in Figure 2 can be replaced with stem 4 in Figure 3.
0, wet conveyor 28, fountain 29 and dry conveyor 32. Similarly, the third
The press shown may be used in conjunction with 7-11 of FIG. The coated can is then ready for any additional internal spray coating or external coating as desired.

The term coating material with reduced water content refers to solvents, emulsifiers,
and dispersions in water.

One such reduced water content coating material that we conveniently use for multi-stage wall ironing of tin cans is a 2 to 10% (volume) solution of a water-miscible co-solvent. In this case, this co-solvent contains ethyl acrylate.
A styrene-acrylic acid copolymer (eg, INQM1574 from Coates Brothers Limited) is dissolved. Such reduced water content coating materials are less viscous solutions. Similarly, we used (cross-linkable modified) acrylic dispersions (e.g.
Pinch Jeongson Limited product NQO966
C-8010R2) successfully carried out this step. Alternatively, reagents may be added to suppress foaming of the coating material in the press. The cans coated with these coatings were placed in a drying oven at 204 C (400'1?) for 1 to 3 minutes to cure the coatings. Instead of being based on acrylic resins, water thinning coatings based on vinyl or other resins such as esters may be used, and these coatings may be colored with dyes if desired. The good thing is that it can be inferred.
The coating applied after the pressing step may be colored. As described above, according to the present invention, a coating material with reduced water content is applied to a workpiece at least during ironing, and this coating material is used as a lubricant and a cooling agent during ironing, and also hardens after ironing. Since the coating material acts as a coating material, there is no need to wash off the applied lubricant or coolant and then apply a new coating material, as in the past.
Therefore, the number of steps is reduced, productivity is increased, and the cost of the coated cans manufactured is also reduced. It should be noted that the surface finishes obtained according to the present invention are already receptive to printing inks and lacquer, making cleaning prior to such steps unnecessary and making it possible to clean sheet materials such as aluminum, steel sheets and tinplate sheets. It has wide application for manufacturing articles by pressing operations.

[Brief explanation of drawings]

1 is a block diagram showing the method according to the invention; FIG. 2 is a schematic diagram of an apparatus for carrying out the first method shown in FIG. 1; and FIG. 3 is a block diagram showing the second method shown in FIG. 1 is a schematic diagram of an apparatus for carrying out the method; 1... Press, 2... Punching rod, 3
...Material holder, 4...Dice, 5.
...Corop body, 6...Koppu body that came out of the die, 17,18...Ring for ironing, 2
0...Bottom molding block, 30...Cop body, 31...Cot type body that came out of the die, 32
...Dry belt, 33...Press,
34...Punching rod, 35...Material holder.

Claims (1)

[Claims] 1. A process of making a work piece from sheet metal, a process of drawing this work piece into a cup, a process of re-drawing the drawn cup into a deeper cup, and a process of ironing the wall of the deep cup. In this method, a coating material with reduced water content is applied to the work piece during and after the ironing process, and this coating material is used as a lubricant and cooling agent during the ironing process, and is used as a lubricant and cooling agent during the ironing process. It is characterized in that it acts as a covering material that can be cured later, and that the cup is moved vertically upward or rotated while the cup is sent to the drying process after ironing to cause droplets attached to the outer surface of the cup to fall. A method of manufacturing a coated can.