Title:
Continuous anodizing and coloring process
Kind Code:
A1


Abstract:
A process and apparatus for conducting an electrically independent current through an anodized web to electro-deposit a coloring agent on the web. A preferred process includes the step of providing a continuous web of anodized aluminum; transferring with a charging plate a coloring current to the web with a charging plate in a first treatment cell over an area of the web sufficient to allow the current to pass through an anodic layer of the aluminum and flow through the web; and electro-depositing coloring agents on the web with the coloring current in a second treatment cell. Optionally, the web may be serially passed through additional treatment cells to apply a variety of different coloring currents to the web whereby the web may be colored with multiple coloring agents and consequently exhibit multiple colors and/or refractive properties.



Inventors:
Marczak, Gregory S. (Fruitport, MI, US)
Minner, Rick A. (Muskegon, MI, US)
Application Number:
09/766356
Publication Date:
07/25/2002
Filing Date:
01/19/2001
Assignee:
MARCZAK GREGORY S.
MINNER RICK A.
Primary Class:
Other Classes:
205/96, 205/102, 205/139, 205/150, 205/213, 205/324, 204/206
International Classes:
C25D11/22; (IPC1-7): C25D5/00; C25D5/44; C25D7/06; C25D11/04; C25D11/16
View Patent Images:



Primary Examiner:
LEADER, WILLIAM T
Attorney, Agent or Firm:
WARNER NORCROSS + JUDD LLP (GRAND RAPIDS, MI, US)
Claims:

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:



1. A process for continuously anodizing and coloring a web of aluminum comprising the steps of: applying an anodizing current to the web; and applying an electrolytic current to the web wherein the electrolytic current is non-coincident with the anodizing current.

2. The process of claim 1 wherein a first coloring agent is deposited on the web during said electrolytic current applying step.

3. The process of claim 2 further comprising the step of repeating said electrolytic current applying step to deposit at least one second coloring agent on the web.

4. The process of claim 3 further comprising the step of controlling the application of the electrolytic current to the web to selectively control the deposition of at least one from the first and second coloring agents on the web.

5. The process of claim 2 further comprising the step of controlling the application of the electrolytic current to the web to selectively control the deposition of the first coloring agent on the web.

6. The process of claim 5 wherein the step of controlling the application of the electrolytic current includes adjusting one chosen from the amplitude, frequency, duration of application, and bias of the electrolytic current.

7. A process for continuously coloring anodized aluminum comprising the steps of: providing a continuous web of aluminum having an anodic layer; applying a coloring current to the web over an area of the web sufficient to allow the coloring current to pass through the anodic layer and conduct through the web; and electro-depositing a coloring agent on the web.

8. The process of claim 7 further comprising the step of repeating said electro-depositing step.

9. The process of claim 7 wherein the coloring agent is capable of being secured to the continuous web in a plurality of configurations, each configuration causing the web to refract light in a particular manner.

10. The process of claim 8 further comprising the step of controlling the refractive orientation of the coloring agent electro-deposited on the web.

11. The process of claim 8 further comprising the step of subjecting the web to at least one chosen from cleaners, detergents, etching solutions, and desmutting solutions.

12. A process for anodizing and electro-depositing materials on a continuous web of aluminum comprising the steps of: applying direct current to the continuous web in a first tank to anodize the web; passing the web by a charging member in a second tank; applying alternating current that is non-overlapping with the direct current to the anodized web with the charging member; and electro-depositing a material on the anodized web in a third tank with the alternating current.

13. The process of claim 12 further comprising the step of controlling the alternating current to manipulate the configuration of the material deposited on the anodized web.

14. The process of claim 12 wherein the material is electro-deposited on the anodized web so that the web refracts light in a first manner.

15. The process of claim 14 further comprising the step of repeating said electro-depositing step.

16. The process of claim 15 wherein the material in the repeated electro-depositing step is deposited so that the anodized web refracts light in a second manner.

17. The process of coloring a web comprising the steps of: providing a continuous web of aluminum including at least one anodic layer; applying a coloring current to the web through the anodic layer at a first station; advancing the web to a second station including coloring agents; and electro-depositing the coloring agents on the web with the coloring current.

18. The process of claim 17 further comprising the step of repeating said providing, said coloring current applying, said advancing, and said electro-depositing steps.

19. The process of claim 18 wherein the coloring current is applied through the anodic layer with a charging plate that imparts a voltage to a surface of the web.

20. The process of claim 19 wherein the charging plate imparts a positive voltage that penetrates the anodic layer.

21. The process of claim 20 wherein the charge is transferred from the plate to the web with the assistance of an electrolyte at the first station.

22. The process of claim 21 wherein the electrolyte is at least one acid chosen from sulfuric, phosphoric, nitric, and acetic acids.

23. The process of claim 22 wherein the second station includes a solution that enhances the application of the coloring current to the web.

24. The process of claim 23 wherein the solution includes salt chosen from tin, cobalt, silver, nickel, manganese, magnesium, selenium, zirconium and copper salts.

25. The process of claim 17 further comprising the step of controlling the refractive orientation of the coloring agents electro-deposited on the web.

26. An apparatus for anodizing and coloring a web comprising: means for producing an anodic layer on the continuous web by application of an anodizing current; and means for electro-depositing a coloring agent on at least one from the web and the anodic layer by application of an electrolytic current wherein said electrolytic current is non-coincident with said anodizing current.

27. The apparatus of claim 26 further comprising a second means for electro-depositing a second coloring agent on the continuous web by application of said electrolytic current.

28. The apparatus of claim 26 further comprising a second means for electro-depositing a second coloring agent on the continuous web by application of a second electrolytic current wherein said second electrolytic current is non-coincident with said anodizing current and said first electrolytic current.

29. The apparatus of claim 23 further comprising at least one additional means for electro-depositing a material on the continuous web by application of at least one additional electrolytic current, said additional electrolytic current non-coincident with said anodizing current.

30. The apparatus of claim 23 wherein said electro-depositing process includes a member that transfers an electrical charge to the web through the anodic layer.

31. An apparatus for coloring a continuous web of aluminum having an anodic layer comprising: means for applying a first voltage current to the web through the anodic layer; means for providing a first coloring agent; and means for applying a second coloring voltage to the web whereby said first coloring agent is affixed to the web.

32. The apparatus of claim 31 wherein said first means includes a charging plate and imparts a positive voltage to a surface of the web.

33. The apparatus of claim 32 wherein the voltage penetrates the anodic layer and is conducted through an inner portion of the web.

34. The apparatus of claim 31 further comprising means for providing a second coloring agent.

35. The apparatus of claim 34 further comprising means for applying a third current to the web whereby said second coloring agent is affixed to the web.

36. The apparatus of claim 35 wherein said first and second coloring agents are affixed by electro-deposition on the web.

Description:

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process and apparatus for anodizing and electrolytically coloring aluminum.

[0002] Currently, anodized and colored aluminum products are desirable because they exhibit many beneficial characteristics such as: resistance to corrosion, chemical staining, and fading; electrical insulation; and exceptional structural rigidity. Anodized, colored aluminum is used for a variety of applications including household appliances, automotive trim, building materials, farm equipment, furniture, sporting goods, cans, and container closures.

[0003] Typically, anodized, colored aluminum is produced in coil form. A coil of untreated aluminum is unwound, processed through anodizing and color tanks, and rewound into a coil. Conventionally, it is most efficient and cost effective to both anodize and color the aluminum in a single multi-step process. It also is possible to anodize and color in multiple, single-step processes, but the web must be rewound between steps.

[0004] Many processes are known for anodizing and coloring aluminum in a continuous manner to produce the coil. In all of these processes, the coloring conditions are dependent on the anodizing conditions and vice versa. A widely-used process and its related apparatus for continuously anodizing and coloring a web of aluminum are illustrated in FIG. 1. A web of raw, unprocessed aluminum 10 is pulled from the coil 8 through the anodizing tank 20 and the electrolytic coloring tank 30. In the anodizing tank 20, the aluminum web is anodized, that is, the surfaces of the aluminum web 11 are oxidized to form an anodic oxide coating or anodic layer. Power source 40 applies positive and negative direct voltage, also referred to as anodizing voltage, to the web. This is done through anodes 44 and cathodes 45 respectively, which conduct the direct current 43 through the solution 22 to and from the web as depicted.

[0005] Next, the anodized web 11 is colored in electrolytic coloring tank 30. In the coloring tank, a coloring current is used to electro-deposit metal salts present in solution 32 on the anodized web. These metal salts are responsible for coloring the anodized web. To electro-deposit the salts, a negative alternating voltage is applied to electrodes 52. A corresponding positive alternating voltage is applied to the web at electrolytic contact 53 (before the anodizing tank 20) and through anodes 44 (in the anodizing tank 20) via the electric conduits 56, 42 and solution 22. Consequently, alternating current (called the coloring current) is conducted through the web 10 and the bath 32 in tank 30. It is necessary to apply the negative alternating voltage at electrolytic contact 53 and through anodes 44 before the web 10 is coated with an anodic layer near the cathodes 45, because the anodic layer is insulative.

[0006] This is more readily understood with reference to FIGS. 2 and 3. As seen in FIG. 2, the web 10 is in its raw aluminum sheet state, and current can flow freely into the web 10 as depicted. FIG. 3 depicts web 11 at a point near the cathodes 45 after it has been anodized to form anodic layers 18 having pores 12. The anodic layer 18 is an insulator, and does not allow current 19 to pass easily therethrough. The current 57, however, can flow freely through the web 11 under the anodic layer, that is, in core 13 as shown. Thus, it is necessary to apply coloring current to the web before its surfaces are completely anodized so that the current can flow through the web to the coloring tank.

[0007] Although conventional anodizing and coloring processes and apparatus are effective, they suffer a variety of shortcomings. First, the anodizing conditions and coloring conditions are inseparably dependent on one another because the direct and alternating currents for anodizing and coloring, respectively, are continuously and simultaneously applied to the web. For example, with reference to FIG. 1, in the anodizing tank, anodizing voltage 43 is coincident on the web simultaneously with coloring voltage 57. Due to this overlap, nearly all adjustments of coloring parameters require simultaneous adjustment of the anodizing electric current. Further, any adjustments of the anodizing current affects the coloring parameters. For example, if coloring parameters such as the coloring speed, the uniformity of coloring, or the intensity of coloring are modified, it is necessary to adjust not only the coloring current in the coloring tank but also the anodizing current in the anodizing tank. Likewise, if anodizing parameters such as anodic layer thickness or porosity require alteration of the anodizing current, the coloring current applied in the coloring tank also must be adjusted to maintain the desired coloring.

[0008] More generally, the simultaneous application of the anodizing current and coloring current to the web adversely affects the optimization of coloring conditions. The application of the anodizing current to the web makes the coloring current more “positive.” For example, with reference to FIG. 1, positive coloring current line 56 connects to anode 44 through positive anodizing current line 42. The coloring current is made more positive because it piggybacks on the positive anodizing current in the anodizing current line 42. It is known that better color agent deposition in the anodic layer is obtained when the coloring current is not shifted to be more positive. Accordingly, when the anodizing current makes the coloring current more positive, the subsequent coloring process suffers.

[0009] Third, the apparatus for anodizing and coloring requires the use of resistors to control the simultaneous application of anodizing current and coloring current to the same web. As depicted in FIG. 1, resistor 60 frequently must be replaced with resistors of varying resistance in order to optimize and control the coloring conditions when adjusting the anodizing current or coloring current. Moreover, the resistors must be replaced when treating webs of varying thickness. For example, thin sheets offer little resistance to current flow, thus resistors offering significant resistance must be used with these thin sheets so the web is not damaged by the current. When a thick sheet is to be treated, resistors of less resistance are necessary because the thicker sheets naturally offer more resistance to the current flowing through the web. Accordingly, it is necessary to frequently change resistors when treating webs of varying thickness. This is time consuming and complex, as the resistors must be carefully selected based on web thickness.

[0010] Fourth, it is extremely difficult to color thin continuous webs of aluminum using conventional anodizing and coloring techniques. With thin webs, that is, less than 0.015 inches thick, it is difficult to conduct coloring current over significant distance. Thus, it is typically not feasible to conduct the coloring current from a contact point before the anodizing tank. Moreover, with relatively thin coil sheets, small changes in the coloring current introduced at the pre-anodizing contact point result in significant changes in coloring efficiency in the coloring tank. Additionally, small changes in the anodizing current at the anodizing station also effect the electrolytic coloring current which subsequently effects the coloring efficiency.

SUMMARY OF THE INVENTION

[0011] The aforementioned problems are overcome in the present invention for a continuous coloring process and related apparatus wherein electrolytic coloring is carried out is using an electric current that is independent of the anodizing current. More particularly, in an anodizing and coloring process, coloring current used in the coloring step is applied to a continuous web after the web has been anodized so that the coloring current is electrically isolated from the anodizing current and not adversely affected thereby.

[0012] In general, the present invention includes the steps of: providing a continuous web of anodized material; conducting current through the anodized web in a first coloring tank wherein the coloring current is independent from other electrical currents; and applying a coloring agent to the anodized web with the current in a second tank. Adequate coloring current is conducted through the anodized web by increasing the electrical contact area/surface of the web.

[0013] The following steps are included in a preferred embodiment: anodizing aluminum web to create an anodic layer at an anodizing station with an anodizing current; transferring a coloring current to the web through a relatively large area of the anodic layer; and electro-depositing at least one coloring agent on the web with that coloring current. Preferably, the coloring current loop is entirely downstream of the anodizing process so that the coloring current is electrically independent from or non-coincident with the anodizing current.

[0014] Optionally, the present invention may include a plurality of serial coloring steps whereby multiple coloring agents having different colors and/or refractive properties are deposited on the web. For example, after a first coloring agent is electrolytically deposited on the anodized web in a first coloring tank, the web may be advanced to a second coloring tank wherein a second coloring agent is deposited on the web. The first and second coloring agents may be of different colors or have different refractive properties.

[0015] In another aspect of the invention, different currents having different electrical profiles, for example, different voltage amplitudes, biases, and/or frequencies, may be used to serially deposit the same coloring agent differently at the same or different coloring stations so the web exhibits different refractive properties. For example, a coloring agent having refractive properties may be first deposited with a special electrolytic current that causes the agent to align on the web so that light normally projected onto the web is reflected normal to the web. Subsequently, the same coloring agent again may be deposited with a different electrolytic current that causes agent to align on web so that light normally projected onto the web is refracted 30° from normal to the web. Of course, multiple coloring agents with different refractive properties may be deposited in any desired manner so that light is refracted at any desired angle or number of angles from the finished anodized, colored web.

[0016] The present inventive process and related apparatus provides a variety of distinct benefits. First, coloring conditions can be altered independently of anodizing conditions. Altering the anodizing current has little or no effect on the electrolytic current used to color the web at subsequent coloring stations. Likewise, adjusting electrolytic coloring current in the coloring station has little or no effect on the anodizing conditions at the anodizing station.

[0017] Second, given that the anodizing current and the electrolytic coloring current are electrically isolated from one another, the complexity of the system is reduced. For example, there is no need to use resistors to control overlap of the anodizing current and the coloring current in webs of varying thickness.

[0018] Third, the present invention may be used to apply a variety of color agents and/or refractive materials to a web of anodized aluminum. Accordingly, more aesthetically pleasing and novel coloring and/or refractive schemes for anodized and colored aluminum are possible.

[0019] These and other objects, advantages and features of the invention will be more readily understood and appreciated by reference to the detailed description of the preferred embodiments and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a plan view of an anodizing and coloring apparatus of the prior art;

[0021] FIG. 2 is a detail of an electrode transferring electrolytic current to a web according to a process of the prior art;

[0022] FIG. 3 is a detail of electrolytic current conducted through an anodized aluminum web according to a process of the prior art;

[0023] FIG. 4 is a detail of deposition of coloring agents on an anodized web according to a process of the prior art;

[0024] FIG. 5 is a plan view of the process and apparatus of the present invention;

[0025] FIG. 6 is a detail of electrolytic charge being transferred to the anodized web;

[0026] FIG. 7 is a detail of anodized aluminum having a coloring agent aligned thereon;

[0027] FIG. 8 is a detail of anodized aluminum having multiple coloring agents aligned thereon;

[0028] FIG. 9 is a graph of a coloring current waveform;

[0029] FIG. 10 is an alternative embodiment of the present invention;

[0030] FIG. 11 is a detail of a coloring agent selectively oriented on the anodized web; and

[0031] FIG. 12 is a detail of multiple coloring agents selectively oriented on the anodized web.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032] A first embodiment of the present invention is depicted in FIG. 5 and generally designated 2. The anodizing and coloring apparatus 2 includes 2 stations; the anodizing station 4 and the coloring station 6. The anodizing station includes anodizing tank 120 having anodes 144 and cathodes 145 disposed in an anodizing electrolytic solution 122. The anodes and cathodes are respectively connected to a power source 140 that preferably provides a direct current to the anodes and cathodes. The electrolytic station or coloring station 6 generally includes wet cell 200 and electrolytic coloring tank 130. Both the wet cell and the coloring tank are in electrical communication with power source 150, which is preferably an alternating current source.

[0033] In FIG. 5, the coloring current is independent from, isolated from, or non-coincident with the anodizing current. As can be seen, coloring current loop 201 is non-coincident with or does not overlap the anodizing current loop 143. Subsequent coloring current loops (not shown) are similarly non-coincident with anodizing current loop 143. Accordingly, adjustment of the coloring current does not require simultaneous adjustment of the anodizing current when modifying coloring characteristics or conditions.

[0034] With this electrical configuration, the electro-deposition of coloring agents with coloring current in the coloring tank 130 may be controlled without simultaneous adjustment of the anodizing current in the anodizing station. Moreover, the coloring current is not directly affected by the anodizing current. Specifically, when alternating current is used as the coloring current, the wave cycles of this alternating current are not made significantly more positive or more negative by the anodizing direct current as explained in further detail below. As used herein, “coloring current” means the electrical current used to electro-deposit coloring agents on the aluminum or on an anodic layer thereof. Coloring current may be further comprised of negative and positive voltages used to electro-deposit coloring agents. “Anodizing current” means the electrical current used to anodize aluminum, and it may be comprised of positive and negative currents. Anodizing and coloring currents may be either direct or alternating currents, as known in the art, but preferably, the anodizing current is direct current and the coloring current is alternating current.

[0035] In the preferred embodiment in FIG. 5, the web of aluminum 110 is pulled off from coil 108 which is simply a rolled coil of aluminum sheeting. As used herein, “aluminum” means aluminum or any aluminum alloy. “Web” means aluminum in the form of a strip, wire, sheet, foil, strand, or other configuration that allows for continuous treatment of a length of aluminum. The web 110 feeds through the anodizing station 4 via guides 116. As depicted, the anodizing station 4 includes anodizing tank 120. Power source 140 supplies positive and negative current to anodes 144 and cathodes 145 via connectors 142 and 141 respectively.

[0036] Anodizing tank 120 includes conventional anodizing agents such as sulfuric, oxalic, chromic, and/or phosphoric acid solutions with acid concentrations from about 0.1% to about 60%, or any other concentration suitable for anodizing.

[0037] As will be appreciated, the anodizing web may undergo pre-anodizing treatment (not shown) such as cleaning, etching, degreasing, or desmutting the aluminum web in conventionally known manners.

[0038] In the preferred embodiment, after the web, now 111, which was originally in the form of aluminum, includes an anodic layer on all surfaces of the web that were exposed to the electrolyte 122 in the anodizing tank 120, as will be appreciated by those skilled in the art.

[0039] Next, with reference to FIGS. 5 and 6, the web 111 is guided through the coloring station 6 via guides 116. The coloring station 6 preferably includes an independent treatment cell or wet cell 200 and a coloring tank 130, also referred to as electrolytic coloring tank or electrolytic tank. The wet cell 200 includes a charging plate 204 that transfers voltage or electrical charge to the web 111. The plate is preferably made from a metal, for example, stainless steel, titanium, platinum, copper, or other metal capable of conducting voltage or current. The plate may be of any shape or configuration including a plurality of aligned bars or members. The plate preferably is sized to transfer an electric current to the web 111, through the insulative layer 118, across a portion of the web so that the current C may be conducted through the web core 113. Although the plate may be of any dimensions depending on the size of web treated, it is preferred that the plate be sized so that it may transfer current to a surface of the web that is preferably more than 10%, more preferably more than 30%, and most preferably more than 50% of the total surface area of the web submerged in the conductive solution 202 of the wet cell 200. As indicated, the plate carries a positive charge. Preferably, the plate is in electrical communication with power source 150 via connector 155.

[0040] As depicted in FIG. 5, the wet cell 200 includes a solution 202 that facilitates the transfer of charge or current from plate 204 to the anodized web 111 through any anodic layers on the web. Preferably, the solution includes an acid chosen from sulfuric acid, phosphoric acid, nitric acid, and acetic acid. Concentrations of these acids in the solution 202 are preferably between about 0.1% and about 50%, and more preferably 0.1% to about 10%. The preferred acid in the wet cell solution is sulfuric acid. Notably, concentrations of acid significantly greater than the preferred range will dissolve the anodic layers, and extremely low concentrations, below the lowermost limits of the range of acid concentrations will significantly reduce the conductivity of the solution. The wet cell solution 202 is further preferably maintained at temperatures from about 40° Fahrenheit to about 1800 Fahrenheit, more preferably from about 60° Fahrenheit to about 150° Fahrenheit and most preferably from about 68° Fahrenheit to about Fahrenheit. Temperatures significantly greater than the preferred ranged may deteriorate the anodic layer; and temperatures significantly less than the preferred range significantly impair the conductivity of the solution.

[0041] FIG. 6 depicts a transfer of coloring current, preferably DC voltage, from the plate 204 to the anodized aluminum web 111. As depicted, the charges 206 are transferred through the wet cell solution through the pores 112 of the anodic layer and ultimately to the core portion of the anodized web 111 as depicted. This is possible given the relatively large area over which the plate 204 transfers current 206 through the solution, through the insulative layer 118, ultimately to the core 113. The charges 206 head in direction C through the core 113 given the electrical potentials applied in the wet cell 200 via charging plate 204 and the coloring cell 130 via electrodes 152.

[0042] Optionally, a buffering tank (not shown) may be positioned between the wet cell 200 and the coloring tank 130 to neutralize the acid to which the web 111 was subjected to in the wet cell 200. This buffering tank may include any composition capable of rinsing or neutralizing any acid from the web 111 before it enters the coloring tank 130. For example, the buffering tank may include deionized water maintained at a pH of about 2 to about 7. More preferably, the buffering tank includes deionized water at a pH of about 3 to about 6. With this optional buffering tank, the coloring conditions in the subsequent coloring tank 130 may be more closely controlled, that is, the coloring solution 132 may retain a relatively uniform composition and pH. This in turn enhances uniformity of coloring.

[0043] In the preferred embodiment, from the wet cell 200, the web 111 is guided via guides 116 through the coloring cell 130. The coloring cell includes electrodes 152 that are in electrical communication with power source 150 via connector 154. Preferably the electrodes conduct a negative voltage as indicated. In the electrolytic coloring tank is coloring solution 132 that includes any conventional coloring agents.

[0044] As used herein, “coloring agents” means any coloring and/or refractive material. Coloring materials may include conventional coloring salts such as tin, nickel, cobalt, iron, magnesium, zinc, selenium, zirconium, manganese, or any other salt used to color metals in an electrolytic coloring process. These salts may be present in the coloring solution at a concentration from about 0.1% to about 50%, and preferably, about 0.1% to about 20%. In a preferred solution, tin or cobalt salts are present in concentrations of about 50 to about 150 grams per liter of solution. Refractive materials, also a coloring agent, may include any materials that exhibit specific light refractive properties or any combination of materials that refract light. For example, refractive materials may include single or multiple materials that when deposited on aluminum in a specific orientation refracts light in a specific manner.

[0045] Additionally, acids may be added to maintain the pH of the solution at a predetermined level. In a preferred embodiment, sulfuric acid is added to maintain pH at about 2 to about 5. Additional acids may be included in the solution to enhance the electro-deposition of the salts onto the anodized web 111. For example, boric acid in concentrations from about 25 to 50 grams per liter of coloring solution 132 may be added.

[0046] The power source 150 of the preferred embodiment generates an alternating current that is transferred to the plate 204 of the wet cell and the electrodes 152 of the anodizing tank 130. As appreciated, alternating current is preferred because of its versatility in electro-depositing coloring agents on materials. For example, the shade of the color may be suitably controlled by varying voltage, the electric current and electrolysis time. Further, uniform coloring with minimal deviation of color is obtainable with alternating current.

[0047] The power source 150 includes meters or other measurement display output devices that may be used to monitor the coloring current applied to the web. These meters may include displays that output the typical sinusoidal voltage waveform (FIG. 3) associated with the alternating current generated by the power source 150. Further, the power source includes conventional controls 157 that may be used to automatically or manually adjust the characteristics of the alternating current applied in the wet cell and the coloring tank. For example, the controls 157 may alter the amplitude and frequency of the alternating current, which, in turn affects the deposition of coloring agents on the web in a known manner. In addition, the controls may bias the alternating current so that it is more negative than positive, as described in further detail below.

[0048] Optionally, the coloring station 6 may include additional coloring tanks, one of which is depicted as 180 in FIG. 5. This additional coloring tank may include different coloring agents in its coloring solution 182 than those coloring agents in the first coloring tank 130. Accordingly, multiple colors may be serially deposited on the web 111. The electrodes 184 of the coloring tank 180 are in electrical communication with the power source 150 via electrical connection 170. As depicted, negative current flows to electrodes 184. The positive charge generated by the charging plate at the wet cell 200 conducts through the anodized web, to the second coloring tank 180 where that circuit is completed to deposit additional or the same, but differently oriented coloring agents, on the anodized web.

[0049] Because the coloring current may be applied to the web anywhere after this web is anodyzed, it is possible to color extremely thin webs of aluminum. For example, it may be possible to anodize and color in a continuous process aluminum web having a thickness of less than 0.015 inches.

[0050] Notably, there is no back-flow of the coloring current from charging plate 204 toward the anodizing tank; so the electrical and chemical conditions of the anodizing tank 120 are unaffected. Likewise, there is no flow of anodizing current downstream from the anodizing tank toward the coloring station to distort the chemical or electrical conditions of the coloring station. Thus, no compensation of the alternating current used in the coloring station for electro-depositing coloring agents is necessary.

[0051] This effect is especially beneficial when controlling the biasing of the sinusoidal wave form of alternating current generated from the power source 150 to fine tune coloring characteristics or conditions in the coloring tank 130. More negative sinusoidal waveforms representative of the alternating current result in better electro-deposition of coloring agents on the web because the coloring agents more readily convert to a chemical form that associates with the web in the presence of that more negative current. However, it is still preferable to have the alternating current be positive for at least a portion of the time so that the coloring agents evenly deposit on the surfaces. It has been found that if there is not at least some portions of the alternating current cycle that are positive, the coloring agents clump or deposit more heavily on some regions of the web than others.

[0052] For example, in FIG. 9, the X-axis represents time and the Y-axis represents the amplitude of the current. P and N represent the portion of the sinusoidal wave form that generates positive current to the charging plate and the negative current to the electrodes, respectively. A standard sinusoidal wave form 400 of alternating current distributed to the wet cell 200 and coloring tank 130, and optionally coloring tank 180, may be biased to the more negative waveform 402 with commercially available controls 157 (FIG. 5). Of course, the standard alternating current 400 may be biased to have a more positive portion than negative portion or an even more negative portion than positive portion, as depicted depending on the application. Because the anodizing current does not overlap, and therefore affect the coloring current, the anodizing current may be directly adjusted without considering its consequential effect on the coloring current.

[0053] The apparatus of the present invention may also include additional treatment process apparatus such as washing tanks and sealing tanks. The washing tanks may include known solutions to wash the chemicals from the aluminum web after it has been anodized and colored. The sealing tanks may include commercially available sealing solutions for anodic coatings as will be appreciated by those skilled in the art. The apparatus may further include a recoiler (not shown) for rolling the web into an easily transportable form.

Method of Manufacture

[0054] The preferred process of the present invention includes anodizing a continuous aluminum web with an anodizing current in an anodizing station and electrolytically coloring the web with a coloring current where the coloring current is electrically independent from the anodizing current. As depicted in FIG. 5, the web 110 is anodized in anodizing tank 120 so that an anodic layer 111 forms on all surfaces of the web exposed to the anodic solution 122 as will be understood by those skilled in the art. The power source 140 is preferably a direct current power source used to distribute direct current to the anodes 144 and cathodes 145 and create an oxidative environment to form an anodic layer.

[0055] After anodizing in the anodizing station, the anodized web 111 is advanced to coloring station 6. In the coloring station, the web is passed through the wet cell 200 and the coloring tank 130. In the wet cell, the web is passed by charging plate 204. Charging plate 204 is connected to power source 150 which preferably generates an alternating current with the positive portion of the current being passed to the charging plate 204. FIG. 6 depicts the positive charge from the charging plate 204 being passed to the core 113 of the anodized aluminum web 111. The wet cell solution 202 acts as a conduit to facilitate transfer of the positive charge 206 from the plate 204 through the pores 112 of the anodic layer 118 of the web 111. After the charges 206 are transferred to the core of the aluminum 113, the core 113 acts as an electrical conduit and the charges 206 travel in direction C downstream toward the coloring tank by virtue of the electrical potential generated by negative charge electrodes 152 exerting electrical forces on the anodized web 111 in the coloring tank. The electrical charge 206 propagates through the core 113 to the electrolytic coloring tank in a conventional manner.

[0056] Once in the coloring tank, the coloring agents in the coloring solution 132 are electro-deposited onto the anodized aluminum web in a conventional manner. As will be appreciated, the electro-deposition may be controlled using controls 157 without outside interference from other currents, such as the anodizing current. Specifically, uniformity, orientation and amount of coloring agents deposited may be closely controlled. Accordingly, coloring agents may be precisely applied to the anodized web.

[0057] With the coloring current separate from the anodizing current, an operator or machine may modify characteristics of the coloring current and consequently coloring properties of the web without taking into consideration any effect of the anodizing current on such modification. More particularly, an operator may adjust the amplitude, frequency or bias of an applied current coloring current directly, without external factors confounding the modification. All of these adjustments may be conducted via the controllers 157 which are associated with the power source 150. These controllers are commercially available from Dynapower Corporation, South Burlington, Vermont. For example, an operator may bias the sinusoidal wave form alternating voltage of the preferred embodiment simply by setting the controller 157 to a selected bias. As depicted in FIG. 9, an operator may make a preferred alternating current more negative, that is, bias the standard current, represented in sinusoidal waveform 400, to a biased current 402, also represented in sinusoidal waveform. Such modification is desirable when controlling the orientation of the coloring agents as they are deposited on the web 111.

[0058] After the coloring agents have been electro-deposited on the anodized web, the anodized web becomes an anodized, colored web 115. As depicted in FIG. 7, the coloring agents 114 are deposited in the pores 112 of the anodic layers 118 of the anodized web 115. It will be appreciated that the coloring solution 132 may include coloring agents that are electro-deposited with different coloring currents. With the present invention, these different coloring agents may be sequentially electro-deposited in a single coloring tank. An operator need only adjust the coloring current to cause each particular coloring agent to electro-deposit on the web. It will further be appreciated that single coloring agents having a potential to electro-deposit in a plurality of specific orientations under different coloring currents may also be deposited with the present invention. For example, a first coloring current may be applied to cause a coloring agent to electro-deposit in a first specific orientation and offer a first refractive characteristic, referred to as a “refractive orientation.” Then, a second coloring current may be applied to cause the same coloring agent to electro-deposit in a second specific orientation and offer a second refractive characteristic. Of course, a single coloring agent may be electro-deposited in a plurality of orientations as desired.

[0059] Optionally, the colored anodized web 115 may be advanced to a second coloring tank 180 and have additional coloring agents electro-deposited onto the anodized colored web. This is preferred in applications where multiple colors are to be applied to an anodized web. The operation of the second coloring tank 180 is the same as that of the first coloring tank 130. The positive charge supplied by the charging plate 204 may similarly be used to assist electro-deposition of the coloring agents in the coloring tank 180. That charge from the plate would simply be conducted through the colored anodized web to the second coloring tank 180. FIG. 8 depicts the anodized web after it has been colored in the first and second tanks with different coloring agents 114 and 119, respectively. As will be appreciated, the anodized web may be advanced to a plurality of additional coloring tanks to apply additional coloring agents or the same coloring agent in a plurality of refractive orientations as the application requires.

[0060] After the web has been anodized and colored as desired, the web optionally may be sealed in commercially available sealing solutions or further processed in any conventional manner. After processing, the web is preferably rolled into a coil for easy transportation.

Alternative Embodiments

[0061] FIG. 10 depicts an alternative embodiment of the present invention wherein multiple coloring stations are used to apply a plurality of coloring agents or select coloring agent(s) in a plurality of predetermined refractive orientations. This apparatus includes a plurality of independent coloring stations 6, 7, 9 having a wet cells 200, 300, 400 and a coloring tanks 130, 330, 430 rather than the single wet cell and one or more coloring tanks in the preferred embodiments. The operation of the systems are similar to that of the preferred embodiment. The power source provides coloring current to the charging plates 204, 304 and 404 in the wet cells 200, 300 and 400 as well as the electrodes 152, 352 and 452 in the coloring tanks. A first coloring agent may be deposited on the anodized web in the first coloring tank 130, a second coloring agent may be deposited on the web in the second coloring tank 330, and a third coloring agent in the third coloring tank and so on as desired.

[0062] In this alternative embodiment, each of the independent coloring stations 6, 7 and 9 include independent power sources 150, 350 and 450 to generate coloring currents for their respective wet cells and coloring tanks. Each of the additional coloring stations 7 and 9 electro-deposit coloring agents onto the anodized aluminum in the manner the same as that in the first coloring station 6. The additional coloring stations may be used to deposit coloring agents of varying color to make a color anodized web having a plurality of colors. As will be appreciated, a single coloring agent may be applied at each independent station in varying refractive orientations as well. Of course, additional coloring stations may be added to add more colors as the application requires.

[0063] With this alternative embodiment, the characteristics of the coloring current applied to the coil at each independent station 6, 7 and 9 are highly controllable. For example, coloring agents that have specific refractive properties may be precisely oriented on the anodic layers of the web. For example, FIG. 11 depicts the web after it has been colored using a specific coloring current in coloring station 6. As evident, the coloring agents 114 are aligned so that they are disposed only on one side of each of the pores 112. The electro-deposition of the coloring agents 114 in the next coloring station 7 may be precisely controlled with the power source 350 so that the coloring agents deposited on the anodized web are aligned as depicted in FIG. 12. The originally deposited coloring agents 114 remain deposited on the first side of the pores in the anodic layer 118; and the coloring agents 119 added in station 7 are disposed on opposite sides of the pores 112. Accordingly, the anodized and colored web 115 depicted in FIG. 12 exhibits different refractive properties, color properties, or shading properties when perceived from different points of view A, B and C. As will be appreciated, other coloring agents may be specifically added in virtually any orientation by simply manipulating the coloring current in each of the coloring stations.

[0064] The above descriptions are those of the preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any references to claim elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular.