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Publication numberUS3922213 A
Publication typeGrant
Publication dateNov 25, 1975
Filing dateOct 23, 1974
Priority dateOct 23, 1974
Publication numberUS 3922213 A, US 3922213A, US-A-3922213, US3922213 A, US3922213A
InventorsDavidson John J, Smith David A, Smith Steven C
Original AssigneeAluminum Co Of America
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and apparatus for uniformly electrocoating the interior of a shaped metal container
US 3922213 A
Abstract
A shaped metal container such as a can is uniformly electrocoated in an inverted position by the insertion of an electrically conducting nozzle therein through which coating material may flow into the interior of the container while an electrical potential is maintained between the container and the nozzle. The nozzle is shaped to direct flow of the material into the corners of the container as the nozzle is inserted and to maintain a transient bath type mode after the nozzle is inserted into the container. Coating material is delivered at a flow rate which permits the can to remain full in an inverted position. When the nozzle is removed the container empties without further mechanical operations.
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United States Patent Smith et al.

1 Nov. 25, 1975 METHOD AND APPARATUS FOR UNIFORMLY ELECTROCOATING THE INTERIOR OF A SHAPED METAL CONTAINER Inventors: David A. Smith, Pittsburgh, Pa.;

Steven C. Smith, Arlington, Mass; John ,1. Davidson, New Kensington,

Assignee: Aluminum Company of America,

Pittsburgh, Pa.

Filed: Oct. 23, 1974 App]. No.: 517,326

Gilchrist 204/ 1 81 Kossmann 204/300 Primary Examiner-Howard S. Williams Attorney, Agent, or Firm-John P. Taylor, Esq.

[57] ABSTRACT A shaped metal container such as a can is uniformly electrocoated in an inverted position by the insertion of an electrically conducting nozzle therein through which coating material may flow into the interior of the container while an electrical potential is maintained between the container and the nozzle. The nozzle is shaped to direct flow of the material into the corners of the container as the nozzle is inserted and to maintain a transient bath type mode after the nozzle is inserted into the container. Coating material is delivered at a flow rate which permits the can to remain full in an inverted position. When the nozzle is removed the container empties without further mechanical operations.

12 Claims, 5 Drawing Figures CONTROL MEANS US. Patent Nov. 25, 1975 Illl CONT 58 MEA METHOD AND APPARATUS FOR UNIFORMLY ELECTROCOATING THE INTERIOR OF A SHAPED METAL CONTAINER BACKGROUND OF THE INVENTION This invention relates to the coating of a container. More particularly, this invention relates to electrocoating the interior of a shaped metal container.

The interior of containers such as cans or the like are usually coated with a material which will protect the contents of the container from reaction with the metal and conversely protect the metal from any attack by the contents. Usually, such materials are applied as sprays or the like using conventional paints having organic solvents therein. This requires preliminary cleaning of the container as well as subsequent drying to remove any liquid remaining from the rinsing portion of the cleaning operation. Furthermore some conventional coating systems require a pretreatment or a conversion coating of the metal, while others result in an uneven coating thickness and, in most instances, such coatings require solvent disposal for organic materials evolved in the coating during drying and baking.

Electrocoating type techniques for coating surfaces are, of course, known in the art. Usually, however, these involve immersion into a bath of coating material and such techniques aretherefore not conducive to high speed production lines such as may be found in, for example, can making equipment. Furthermore, electrocoating processes normally rely on the insulating effect of the buildup of coated material on the surface of the article to ensure uniform coating. That is, the material continues to deposit on the surface of the article until a sufficiently thick insulating layer is built up across the entire surface. This coating buildup, again, takes a finite period of time which is longer than that which would be desirable in a high speed production line.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a system for electrocoating the interior of a container which is suitable for use in high speed production lines. This and other objects of the invention will be apparent from the drawings and description of the invention.

In accordance with the invention, a system is provided for uniformly electrocoating the interior of a shaped metal object which comprises inverting the container, inserting into the container an electrically conducting nozzle, flowing coating material through said nozzle into the interior of the container at a rate which permits the container to remain full in an inverted position, and simultaneously imposing an electrical potential between the container and the nozzle to cause the coating to electrocoat the interior of the container.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view partly in cross section of the system of the invention.

FIG. 1A is a top sectional view of a portion of FIG. 1.

FIGS. 2 to 4 are cross sectional views illustrating in step-wise manner the insertion of the nozzle into the container and the flow pattern of the coating material as it flows through the nozzle into the container.

DESCRIPTION OF THE INVENTION In accordance with the invention a container such as the can illustrated at 2 in FIG. 1, is coated by the insertion therein of a coating nozzle 20. Can 2 is retained in an inverted position by a can holder 10 which comprises a U-shaped portion as best seen in FIG. 1A. The can is retained against the U-shaped portion by a restraining rod 12 which, on an assembly line, is moved against can 2 by suitable means 14 which may be an air cylinder or the like.

An anode assembly is positioned above can 2 having an electrical contact portion 32 thereon. The anode assembly is electrically connected to the positive terminal of a power supply which, in the illustrative embodiment, may be a' battery or the like. After can 2 is positioned in can holder 10, suitable means 34, which may be an air cylinder or the like, movesthe electrode contact portion 32 down into contact with the bottom portion of the exterior of can 2 to provide electrical contact thereto.

Coating nozzle 20 comprises a cylindrical conducting member having a center bore 22 therein through which coating material may flow. The coating material is pumped by pump 54 via conduits 52 and 56 from a tank which is illustrated as positioned beneath the nozzle.

The external diameter of the coating nozzle 20 is selected, as best illustrated in FIGS. 2 to 4, to be slightly less than the interior diameter of the can to be coated. In a preferred embodiment, the difference between the external diameter of the nozzle and the internal diameter of the can to be coated at the closest point between the nozzle and the can is chosen to provide a cross sectional area which does not vary greatly from the cross sectional area of nozzle bore 22, for example not more than about 3 times the bore area. This permits the creation of a satellite or transient bath within can 2 to be achieved by a sufficient flow rate of coating into the can without the use of an unduly large pump resulting in a flooded condition thus permitting the entire interior surface of the can to be bathed and in constant contact with coating material. Alternatively, the denozzle orifice was 0.60 sq. in. and the difference be- ,tween the nozzle cross-sectional area and that of the ,anode assembly 30 onto the external surface of can 2, nozzle 20 is raised by an appropriate means such as an air cylinder 24 to a point of insertion into the interior of can 2. As nozzle 20 enters can 2, relay 44 is activated by a control means 74 and the electrical circuit is completed and the pump 54 activated to begin flowing of coating material through bore 22 into the interior of the container. This increases the coating time by using the time required for full insertion of the nozzle into the interior of can 2 to permit coating of the interior of the can to commence. Alternatively, completion of the electrical circuit can be delayed until full insertion of the nozzle into the can, if desired.

Activation of air cylinders 14, 24 and 34 as well as relay 44 and pump 54 are all controlled by a control means 74 depicted in block form. Control means 74 may comprise a computer or an electro-mechanical device such as timing motor equipped with a series of cams which mechanically activate relays. Such automation control means are well known to those skilled in the art and form no part of the instant invention.

As best seen again in FIG. 3, this initial commencing of the coating is prior to the establishment of what might be termed a fully flooded or bath-like condition as best seen in FIG. 4. As shown in FIG. 3, the area denoted at 46 are air pockets which are created by the shape of the nozzle 20. Nozzle is provided with a concave-like surface 26 at the end thereof which terminates in asharp circular edge 28 to direct the flow of coating material to the corner portions 4 of can 2. These portions, in the particular configuration of the can which is illustrated, would normally be the most difficult to coat because of the normal flow patterns as well as their spacing electrically from the end of the nozzle. By providing the sharp end pointedness of the nozzle 28 the throwing power of the bath to the corner portions 4 of the can are increased. Furthermore, by directing the flow of coating material via the concave portion 26 the flow of coating material to the end 6 of can 2 as well as to the corner portions 4 and the sidewalls 8 all portions of the can to be coated are provided with constant supply of coating material which does not deplete with the coating or plating out of the material as would be true of a static bath with no agitation or flowing of the liquid coating material. Air pockets are also avoided or eliminated by the flowing liquid which sweeps out any bubbles formed.

In the illustrated embodiment, can 2 is provided wt an inner necked portion 9 adjacent the end of the can wall 8. This necked portion 9 is placed on the can to permit subsequent attachment of an end or lid to the can without increasing the overall diameter of the can at the seam or chime to facilitate close stacking. While we do not wish to be bound by any theory of operation, it appears that the neck 9 may provide a restraint for the flow of the material which assists in the maintenance of a bath-like condition as shown in FIG. 4 by decreasing the exit flow rate. While it is recognized that not all containers will have such a neck-like portion 9, this condition, if found to be desirable in other applications, may be simulated or duplicated by the provision of annular groove adjacent the bottom portion of the outer surface of nozzle 20. Such a groove could then be provided with an O-ring which would provide a similar restriction in the overall cross sectional area between the outside diameter of the O-ring and the inner diameter of the container to be coated. Such a construction would result in an additional benefit by the provision of electrical insulation at the point of closest proximity between can and nozzle thus protecting against any inadvertent shorting as well as inhibiting excessive buildup of coating thickness at that point.

In operation then, nozzle 20 is raised into the interior of can 2, the coating material flows from tank via conduits 52 and 56 by the action of pump 54 and, as material flows out of nozzle 20 into the interior of can 2 and down along the outer sidewalls 8 of can 2 to exit from the bottom of can 2. As the material flows out of can 2 it is caught in a catch basin 58 from which it flows via conduit 60 back into tank 50. Thus, very little of the coating material is wasted. in one embodiment the sidewalls of catch basin 58 may extend above the bottom of can 2 to provide a weir effect to insure coating of the bottom and end edge surface of the can..

After an increment as short as second the nozzle is retractd from can 2 via air cylinder 24 or the like, the material may still be permitted to flow, however, from nozzle 20 into can 2 as long as a portion of nozzle 20 is still inside can 2. Likewise, the current path is maintained between can 2 and nozzle 20 by maintaining anode assembly 30 incontact with the can until after cessation of the flow of electrocoating material. In this manner the coating time is extended to include the portions of time or increments of time required to both insert and retract the nozzle respectively into and out of can 2. This permits the uniform application of a sufficient amount of electrocoating material while permitting the coating operation to be carried out on a high speed coating line. For example, the nozzle and holder assembly 10 may be placed on a large conveyor belt or circular type of coating station provided with a plurality of such nozzles and holders, thus permitting a number of cans to be coated simultaneously as they move in circular fashion about a portion of the wheel containing the nozzle. Such arrangements are of course well known to those skilled in the art and are well known for use for example not only in the coating of containers but in the filling and sealing of such containers.

It should be noted here that, while as is stated above, normal coating techniques rely upon the buildup of a sufficient layer of coating on the wall or surface of the article to be coated to provide a uniform coating thereon by the creation of.a sufficient and uniform insulation to provide a limiting film thickness, the present invention envisions the uniform application of a coating which may well be less than that which would provide such a limiting film thickness. However, the particular design of the nozzle and the flow pattern which is created thereby as well as the shape of the nozzle with regard to the shaped configuration of the can assists in the application of a uniform coating without the need to rely on the insulating properties of the deposited coating material. Thus, the nozzle ma'y be withdrawn, the flow of coating shut off, andthe electrical potential shut off by respective activation of cylinder 24, pump 54, and relay 44 to discontinue the coating of the container prior to the buildup'of a sufficient thickness of coating to inhibit further electrocoating.

Thus, by the creation of a satellite ortransient bath, applications have avoided the necessity for immersing the entire container into a coating bath wherein a certain amount of coating material would be deposited andtherefore wasted on the outer surface of the container thus conserving coating material as well as permitting the coating station to be a part of a high speed production line used in forming and processing of cans or other containers or the like. Exotic and potentially slow mechanisms for emptying cans immersed in a bath are obviated. Furthermore, the flowing coating eliminates air pockets and assists in the formation of a uniform film on the container.

Having thus described our invention, what is claimed is:

l. A process for uniformly electrocoating the interior of a shaped metal container which comprises:

a. inverting the container;

b. inserting into the inverted container an electrically conducting nozzle;

0. flowing coating material through said nozzle into the interior of said container at a flow rate sufflcient to fill the container; and

d. simultaneously imposing an electrical potential between said container and said nozzle to cause said coating to electrocoat the interior of said container interior.

2. The process of claim 1 wherein the configuration of said nozzle with respect to the configuration of said container permits said flowing of coating material through said nozzle into said container to create a flooded condition between said container and said nozzle to provide a transient bath.

3. The process of claim 2 wherein the outer configuration of said nozzle is in substantial conformity with the inner configuration of said container to provide a uniform spacing therebetween.

4. The process of claim 3 wherein said flow of coating and said imposition of an electrical potential between said nozzle and said container is discontinued prior to the buildup of a coating thickness sufficient to limit further electrocoating.

5. A process for uniformly electrocoating the interior of a shaped metal container which comprises:

a. inverting the container;

b. inserting into the inverted container an electrically conducting nozzle:

1. said nozzle having a configuration with respect to the configuration of said container which permits said flowing of coating material through said nozzle into said container to create a flooded condition between said container and said nozzle to provide a transient bath; and

2. said nozzle having outer configuration in substantial conformity with the inner configuration of said container to provide a uniform spacing therebetween;

c. flowing coating material through said nozzle into the interior of said container at a flow rate sufficient to flood the interior of the container;

d. simultaneously imposing an electrical potential between said container and said nozzle to cause said coating to electrocoat said container interior; and

e. discontinuing said flow of coating and said imposition of an electrical potential between said nozzle and said container prior to buildup of a coating thickness sufficient to limit further electrocoating.

6. An apparatus for uniformly electrocoating the interior of a shaped metal container which comprises:

a. means for retaining said container in an inverted position;

b. means for coating the interior of said container, said means including an electrically conducting nozzle insertable into said container, said nozzle having a passageway therein adapted to flow coating material into said container;

c. means for simultaneously imposing an electrical potential between said container and said nozzle to cause said coating material to electrocoat said container interior; and

d. means for discontinuing said flow of coating and said imposition of an electrical potential between said nozzle and said container prior to buildup of a coating thickness sufficient to limit further electrocoating.

7. The apparatus of claim 6 wherein the configuration of said nozzle with respect to the configuration of said container permits said flowing of coating material through said nozzle into said container to create a flooded condition between said container and said nozzle to provide a transient bath.

8. The apparatus according to claim 7 wherein the nozzle size is preselected with respect to the container size so that the difference between the inside cross-sectional area of said container and the outside cross-sectional area of said nozzle does not vary from the crosssectional area of the nozzle bore by more than about 3 times the bore area.

9. The apparatus of claim 7 wherein a substantial portion of the sidewall of said nozzle is in substantial conformity with said container adjacent said nozzle sidewall to provide a uniform spacing therebetween.

10. The apparatus of claim 9 wherein at least one means to restrict the flow of the electrocoating from said inverted container is provided.

11. The apparatus of claim 10 wherein said means to restrict the flow of said electrocoating material is an inwardly directed projection on said container.

12. The apparatus of claim 10 wherein said means to restrict the flow of said electrocoating material from said container is an O-ring carried by said nozzle adjacent the end of said container.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3399126 *Nov 2, 1964Aug 27, 1968Ford Motor CoElectrodeposition process and apparatus having conduit electrodes
US3476666 *Feb 8, 1966Nov 4, 1969Metal Box Co LtdCentrifugally operating electrodeposition apparatus and method of use
US3476667 *Apr 25, 1966Nov 4, 1969Scm CorpElectrode assembly used in electrocoating hollow articles
US3849284 *Jul 2, 1973Nov 19, 1974American Can CoApparatus method and valve for electrodepositing a coating on interior surfaces of container bodies
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4025660 *Sep 20, 1976May 24, 1977W. R. Grace & Co.Method of masking, venting and coating the inside of a receptacle
US4094760 *Jul 25, 1977Jun 13, 1978Aluminum Company Of AmericaMethod and apparatus for differentially and simultaneously electrocoating the interior and exterior of a metal container
US4107016 *Jun 20, 1977Aug 15, 1978Standard T. Chemical Company, Inc.Method and apparatus for electro-phorectic coating
US4109027 *Jan 21, 1976Aug 22, 1978W. R. Grace & Co.Electrostatic coating apparatus and method
US4119522 *Feb 17, 1978Oct 10, 1978Standard T Chemical Company, Inc.Nozzle apparatus for electrophoretic coating of interior surfaces
US4163703 *Jul 31, 1978Aug 7, 1979Compagnie Europeenne Pour L'equipement Menager "Cepem"Method of coating the inside surface of a hollow body
US4246088 *Jan 24, 1979Jan 20, 1981Metal Box LimitedMethod and apparatus for electrolytic treatment of containers
US4400251 *Jun 5, 1981Aug 23, 1983Aluminum Company Of AmericaMethod and apparatus for simultaneously electrocoating the interior and exterior of a metal container
US4529492 *Jul 10, 1984Jul 16, 1985Herberts Gesellschaft Mit Beschraenkter HaftungProcess for the coating of hollow bodies open on one side
US4544475 *Jun 27, 1984Oct 1, 1985Aluminum Company Of AmericaElectrocoating apparatus
US4883578 *Jun 26, 1987Nov 28, 1989Metal Box PlcElectro-coating apparatus and method
US5096564 *Aug 27, 1990Mar 17, 1992Cmb Foodcan PlcElectro-coating apparatus and method
US5164056 *Nov 16, 1990Nov 17, 1992Plm Berlin Dosenwerk GmbhApparatus and process for the anodic or cathodic electrocoating of hollow bodies, in particular of cans
US5281819 *Jun 6, 1991Jan 25, 1994Aluminum Company Of AmericaApparatus for nondestructively determining coating thickness on a metal object and associated method
US5409585 *Apr 5, 1993Apr 25, 1995Ppg Industries, Inc.Nozzle arrangement for electrocoating container interiors
US5435899 *Oct 29, 1993Jul 25, 1995Pechiney RechercheMethod, device and apparatus for the surface treatment of metal can bodies, in particular of Al or alloys thereof
US5624540 *Jul 23, 1994Apr 29, 1997Enal AgDevice for the electrophoretic coating of the internal surface of hollow bodies
US7887687Aug 22, 2006Feb 15, 2011Deere & CompanyMethod and system for coating a workpiece
US8524065Sep 19, 2008Sep 3, 2013Metokote CorporationSystems and methods for electrocoating a part
DE2929570A1 *Jul 19, 1979Mar 20, 1980Aluminum Co Of AmericaVerfahren und sonde zum elektrobeschichten von behaelterinnenflaechen
DE4325631A1 *Jul 30, 1993Feb 2, 1995Joergens KlausVorrichtung zum elektrophoretischen Beschichten der Innenoberfläche von Hohlkörpern
DE102007033571B4 *Jul 19, 2007Apr 30, 2009Deere & Company, MolineVerfahren und System zur Beschichtung eines Werkstückes
EP0050045A1 *Oct 14, 1981Apr 21, 1982METAL BOX p.l.c.A method of, and apparatus for, electrocoating
WO1995004170A1 *Jul 23, 1994Feb 9, 1995Klaus JoergensDevice for electrophoretic coating of the inner surface of hollow bodies
Classifications
U.S. Classification204/479, 204/625
International ClassificationC25D13/14, C25D13/12
Cooperative ClassificationC25D13/14
European ClassificationC25D13/14