US 3694336 A
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S pt. 26 1972 Y E. J. FlALA METHOD-FOR CAN ELECTRODEPOSITION Original Filed June 2, 1969 2 Sheets-Sheet l INVENTOR EDWARD J. FIALA BY v ATT'Y.
Sept. 26, 1972 E. J. FIALA. 3,694,336
' METHOD FOR CAN ELECTRODEPOSITION Original Filed June 2, 1969 2 Sheets-Sheet 2 INVENTOR EDWARD J. F IA LA ATT'Y United States Patent C) 3,694,336 METHOD FOR CAN ELECTRODEPOSITION Edward J. Fiala, Oak Lawn, Ill., assignor to Continental Can Company, Inc., New York, N.Y.
Original application June 2, 1969, Ser. No. 829,412, now Patent No. 3,647,675. Divided and this application May 26, 1971, Ser. No. 147,003
Int. Cl. B01k /02; C23h 13/00 US. Cl. 204181 3 Claims ABSTRACT OF THE DISCLOSURE This case is a division of co-pend'mg application Ser. No. 829,412, filed June 2, 1969, now US. Pat. No. 3,647,675 in the name of Edward J. Fiala, entitled Automatic Rotary Electrodeposition Apparatus, and assigned to the same assignee as this invention.
My invention is drawn to a method for automatic rotary electrodepositing material onto cans, and specifically, a rotary electrodepositing method for depositing a coating on can bodies.
In the prior art, it has been the practice to dip can bodies into a solution, lift them out of the solution, and allow them to dry. The apparatus of this method is exemplified by the patent to Kronquest, US. Pat. No. 2,206,778, and assigned to the assignee of the present invention.
It is an object of my invention to provide a method for automatically coating can bodies.
It is another object of my invention to provide a can body feed system for the automatic spacing of cans which are rapidly fed through the system by a conveyor, and to provide can spacing of the coated can bodies at discharge.
It is another object of my invention to give minimal surface contact of the coating apparatus with the can body before, during and after deposition of the surface coat.
It is a final object of my invention to provide a method for synchronized feed of can bodies through a coating bath to give a relatively even coat inside and outside with complete coating of bare metal.
In brief, my invention is a method for automatic coating of cans in which a can feed timing spiral receives cans fed to it in a random fashion and conducts these cans to a feed turret. From the feed turret, the can bodies are passed to a large horizontal wheel ha'ving pockets and the can bodies move downward into a coating solution. As the horizontal wheel turns, the coating material is electrolytically deposited onto the can body. The can body approaches a discharge turret, is lifted out of the solution by the discharge turret and conducts the coated can body to the next operation.
The above and other objects will become apparent from the following description and drawings in which:
FIG. 1 is a schematic diagram of a can feed system, can coating system, and can discharge system.
FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1.
FIG. 3 is a cross-sectional view along line 33 of FIG. 1.
Patented Sept. 26, 1972 FIG. 4 is a top sectional view of the slide taken along line 4-4 of FIG. 3.
My method is best described by the operation of my machine which is designed to take its place in a can production line at a stage after the can bodies have been formed. The following describes the operation of the machine and my method. A conveyor 1 such as a flat top chain, carries flanged cans 2 to the timing spiral 3 shown in FIG. 1. The timing spiral 3 passes the can bodies 2 into the feed turret 4. The timing spiral feed turret 4, main rotating wheel 5, and discharge turret 6 are all synchronized to' facilitate passage of can bodies 2 through my machine. The feed turret 4 is shown with 10 pockets around it. The feed turret 4 is rotated in a counter-clockwise direction to convey can bodies 2 to main rotating wheel 5. A guide 7 of some sort may be used to hold the can bodies 2 in the feed turret pockets 9'. The main rotating wheel 5 rotates in a clockwise direction and has pockets 9 mounted along its outer periphery. Along the lower outer periphery of the main rotating wheel, as seen in FIG. 1, is a first outer guide 10. This outer guide 10 holds the cans 2 in the wheel pockets as they proceed along their path and while the cans are being lowered into the coating liquid. The coating solution moves in the tank at about the same speed as the slides and pockets. There being little relative motion between the can and coating solution, there is a minimum amount of foam or bubbles. After the cans are lowered into the coating liquid, they are secured in place on the main wheel in the wheel pockets 9 by the anodes which surround them so that as they are passed around the middle half of the outer circumference of the main wheel, they are passing through the coating liquid. When the can body is under the surface of the coating solution, electric current is passed through the can in such a way that coating material is deposited on the can. This operation begins at about 12. This process continues until the can body has reached point 13 where the current is discontinued, and the can body 2 starts its emergence from the coating liquid. By this time, a coat has been deposited on the inside and outside of the can body 2 and the turret pockets 9 with their respective can bodies start upward out of the solution. While the can body is emerging from the liquid, an outer guide 14 holds the can body in the wheel pocket against the main rotating wheel. Finally, the can body is conveyed to the area of the discharge turret. When the can body comes to the point 15, the can body is peeled oif the wheel by a fixed permanent magnet 16 located at the discharge turret. The fixed permanent magnet keeps the can body pulled up against the turret wheel until the can body in its circular path has come approximately to the point -17 where the conveyor :1 crosses the can body path as the can is transported by the discharge turret. When the can body comes to the conveyor, it is released by permanent magnet 16 and is carried away by the conveyor to the next operation.
The coating composition used in my apparatus may be a Water-dispersed coating composition, such as a partially neutralized acrylic interpolymer and an amine-aldehyde condensation product or a polyepoxide or both. Examples of such interpolymers are found listed in the patent to Donald P. Hart, US. Pat. No. 3,403,088, and assigned to P.P.G. Industries, Inc.
It is noted that these protective coatings have high dielectric strength, coat metallic articles completely, have eflicient electro-depositing qualities, and result in cured films which are clear, glossy and have attractive appearance and good durability.
Details of the can pockets and can pocket supports are shown more clearly in FIG. 2. When the can body 2 enters the wheel pocket, as shown in detail in FIG. 2, it is supported above and below by support elements. As the can slides by the outer guide shown in FIG. 1, this guide contacts only the outer flange of the can without touching the can body.
In FIG. 2, the wheel pocket is in its upper position. This wheel pocket has two supports 18, 19 one above and one below, and the can 2 is contained in between them. Can 2 touches the wheel pocket only at the edge of the can. In this way, the can surface exposed to coating is at a maximum. The position shown in FIG. 2 is the position of the slide 20 on the slide support shaft 21 when the can has just entered the pocket of the main wheel. The can is in this position also just before it is about to exit from the pocket of the main wheel. In each of these cases, the roller 22 is in position at the top of the roller track 23 as shown. The roller track 23 is part of the slide cam 24 and has a continuous path varying in amplitude from the top of the slide cam to the bottom of the slide cam. As the roller follows the roller track from the top of its path to the bottom, the pocket is pushed down into the solution. As the main wheel rotates, the roller follows the roller track down the slide cam forcing the slide and the wheel pocket with the can body to descend to the bottom of the slide shaft. At the point that the can body is at the bottom of the slide, FIG. 3, the can flange touches three anodes 11 which are spaced around the can position so as to press somewhat against the flange 22 of the can. That is to say, the can body is a force-fit between the anodes. As this station with its can proceeds around the slide cam, the wheel pocket and can are lowered into the lowermost position. Electric potential is applied across the cathode 25 to the can body when the flange of the can makes electric contact with the anodes. Slip rings or some other conventional means mounted at the center of the main wheel provide a connector for electrical current from the electricity source to the anodes and cathodes. The anode and cathode are mounted on an insulator member or support plate 26. The anodes and cathode stay in the solution and the only relative motion between electrical conductive elements is at the slip rings. The can body is press fitted down between the anodes when the slide cam is at the bottom of its shaft. As the can body slides down between the anodes, the sharp edge of the flange 22 cleans the contact area of the anode and a good electrical contact is maintained between the anode and the can flange. The non-contact surface of the anode is coated rather quickly by electrolytic deposition. After the anode is coated, little or no electrolytic deposition takes place on the anode, but only on the surface of the can body.
By keeping the anodes and cathodes continually in the solution, only a very thin layer of coating material is applied to them, since the wet solution does not dry on the electrodes.
When the can descends into the area between the anodes and touches the bare surface of one or more of the three anodes, the electric potential from the can to the cathode becomes the same as the electric potential between the anodes and the cathode. The surface area of the can is relatively large and since the can is located somewhat nearer to the cathode than any of the anodes, and the anodes are coated, the can body receives coating which is deposited on the bare surfaces of the can body because of the electric potential across the cathode and the can. The length of the cathode is about coextensive with the can length. The application of electric potential across the cathode and can body sets up an electric field between the cathode and anode to cause migration of ions from the cathode to the can body and consequent electrolytic deposition of a coating material on the can body. Most of the coating material is deposited upon the inside of the can body. Fresh solution is assured because the can body is being swirled through the coating solution and currents are continually pasing through the interior of the can body as well as by its exterior. The
exterior of the can receives some coating upon it from the ions of the coating solution which are mixed with the electrically neutral coating solution located outside the can body.
When a can body has completed its coating cycle and has arrived at point 13, FIG. 1, it will start its journey out of the solution. The can body flange 22 moves upward on the slide and when it clears the anode, the electrical potential is disconnected between the can body and anode and no more coating material is deposited on the can because the can is electrically neutral. Likewise, the discharge of current between the anode and cathode directly coats the anode with an insulating coating and as soon as the three anodes have been coated on their can flange contact spots, electric current will cease flowing from cathode to anode at this station.
Alternatively, electric potential switching action may be applied across the cathode and anode by means of limited segmented slip rings at the center of the main wheel. In any case, after the can is lifted, no more electrolytic deposition takes place across the anode and cathode until a new can body is press fitted down into the space between the anodes and the can body is electrically connected to the anode and thus, to the electric power source through the can flange and the bare spot on the anode. The coated can body is now lifted out of the solution and comes to the discharge turret. At this point, the can body is at the same elevation as the discharge turret and the discharge turret magnet peels off the can body from the wheel pocket.
As pointed out in the description of FIG. 1, the coated can body is transferred smoothly into the discharge turret pocket and revolves with the discharge turret 6. The outer guide 28 acts as a safety feature to hold can bodies to the discharge turret where the magnet fails. However, in normal operation, the coated can bodies do not touch the outer guide 28 because it is essential to minimize scraping contact which might cause the loss of coating from the can body.
The top view of the pocket and side of FIG. 4 shows the two slide supporting shafts 21 upon which the pocket slides. The top plate 18 of the pocket and the bottom plate 19 of the pocket are shown one above the other. The anodes and cathodes are mounted in the insulating plate 26, and the insulating plate is shown as mounted and supported by vertical shaft 27 which is attached to the wheel as shown in FIG. 2.
Some of the advantages of my invention are that vertical entry of the can body prevents air bubbles from forming within the can bodies, can bodies are uniformly separated in the deposition cycle, can bodies are coated evenly and completely inside and outside, only the bare conductive metal of the can body is coated, little material is used, the system has an automatic electric on/oif feature, the solids of the coating solution are kept in suspension by the stirring action of the rotating slides and pockets, and the electrical system elements are fixed in position.
The foregoing is a description of the illustrative embodiment of the invention, and it is applicants intention in the appended claims to cover all forms which fall within the scope of the invention.
What is claimed is:
1. A method of electrodepositing a coating solution onto a flanged can body comprising:
moving said can body in a circular fashion about a central hub;
swirling said solution in a circular fashion in the same path as said can body and at the same speed as said can body;
lowering said flanged can body into said solution having an electrodepositing material therein, whereby few bubbles adhere to said can body;
applying an electric potential between an anode and a cathode located in said solution;
forcing the flanged can body down between spaced vertical anodes, whereby said anode and a can flange form an electrical contact; and
raising said flanged can body from said coating solution.
2. A method of electrodepositing a coating solution onto a flanged can body as set forth in claim 1 in which the step of forcing said flanged can comprises the steps of:
pushing said flanged can down between the anodes whereby the flange of said can touches each said anode;
scraping the flange of said can body against the side of each said anode whereby an electrical contact is established between said can body and said anode.
3. A method of electrodepositing a coating solution onto a flanged can body as set forth in claim 2 in which the step of raising said flanged can body comprises the steps of:
lifting said flanged can body from between said anodes whereby the flange and anode are electrically discon- References Cited UNITED STATES PATENTS Clayton et al. 204-181 Sumner et al. 204-181 Sumner et al. 204-181 X Clayton et al. 204181 Jackson et al. 204-300 Bell et al. 204-481 JOHN H. MACK, Primary Examiner A. C. PRESCOTT, Assistant Examiner US. Cl. X.R.