US3374165A - Conductor roll - Google Patents

Description

March 19, 1968 J w, o' L 3,374,165

CONDUCTOR ROLL Filed Feb. 18, 1965 Es. am A United States Patent 3,374,165 CGNDUCTOR ROLL John W. Ollrien, Villa Park, and Arthur R. Stahllicrg, Park Ridge, ilk, assignors to Electra-Coatings, Inc, a corporation of Delaware Filed Feb. 18, 1965, Ser. No. 433,68$ 14 Claims. (Cl. 204-479) This invention relates to conductor rolls for use in electric coating operations and to the manufacture of such rolls. More particularly, this invention relates to a conductor roll having a seamless roll surface which can be used as an electrode in electrolytic plating or cleaning of sheet steel or the like for forming such products as tin or galvanized plate.

It is common practice to use a conductor roll as the electrode in continuous electrolytic cleaning and plating processes for coating metal from a solution or molten metal bath onto low carbon steel sheet to form tin or galvanized plate. Usually, solution plating, for example is carried out using high speed plating baths of the plating solution. The stock or sheet material to be plated is passed through the bath and held immersed in the bath during its passage therethrough by the conductor roll. An anode is placed on the other side of the stock from the conductor roll and spaced close to the roll. A low voltage, e.g., -30 volts, power source is connected between the anode and the conductor roll, which functions as the cathode, to establish a direct current field between the anode and cathode and through the solution and stock sheet. In solution plating procedures, the direct current field is usually in the range of 400 to 800 amps er square foot. Normally, when the solution is a tin plating solution, for example, the direct current field will be snfficient to establish a current density of abnut 400 amps per square foot; and, when the solution is a zinc plating solution, 500-600 amps per square foot are usually suilicient. Bath or solution temperatures normally range from 90 F. to 160 F.

The sheet or stock material is usually pulled through the cleaning and plating baths at a high rate of speed, and the line tension can be as much as 4,000 pounds or more. Such tension may be generated by an applied weight at the drag bridle station which magnifies through hydraulic reaction against the stock material passing through the cleaning and plating tanks. Such line tension creates stresses on the shaft on which the conductor roll is mounted since the tension is applied against the roll face as the stock material is pulled through the bath.

Further, the constant exposure of the conductor roll to acids in the plating bath and severe friction and heat generated by the electrical current and heat of the plating bath, in addition to tension, present problems with respect to conductor roll life and roll maintenance. The

conductor roll must have excellent thermal and electrical properties. Carbon rolls, which have a thick (e.g., 4 inches) layer composed of carbon and a resin binder applied to an inner shell or shaft and have acceptable electrical properties, have been used as conductor rolls, but they are costly and susceptible of excessive wear.

It has been common practice to incorporate the very highly conductive metals, such as copper, in conductor roll designs. In another prior art structure, roll trunnions are constructed of still-cast copper while the roll body is formed from rolled and welded copper plate or cold drawn seamless copper tubing. To protect the copper surface against corrosion and erosion, the roll surface can be metalized with stainless steel metal spray. Such stainless metalizing has not been very successful because the applied metals do not have the hardness, bonding characteristics and dense grain structure required to transmit 3,374,165 Patented Mar. 19, 1968 current and resist wear and corosion; wear caused by the stock sheet passin over the conductor roll increases the porosity of the stainless steel surface layer, resulting in picking up and retention of acids which eventually erode the stainless steel coating with resulting roll failure. Also, where protective layers are deposited by spraying metal on a roll surface of copper, the copper is porous and does not have consistent hardness. This condition creates hot spots which eventually cause failures in the bond between the copper surface and protective layer, resulting in roll failure.

In one successful approach, a conductor roll has been constructed having a body portion entirely of steel. The journals are sleeved with still-cast copper, and the roll body is electroplated or sprayed with metal to retain a substantial thickness, e.g., inch, of copper; and the copper surface is then electroplated with chrome or nickel to prevent corrosion. Although such roll has been successful in operation, its construction is very expensive and the roll still presents many maintenance problems, such as loss of the protective coatings of chrome or nickel after such coatings have become scored or gelled through use.

It has also been attempted to apply a rolled and welded stainless steel shell over a roll face; but it has been found that the Weld, when exposed to acid, would discolor and mark the stock sheet being processed, causing undue rejections. Further, such rolled and welded structures have poor tolerances with respect to roundness and require the use of a very heavy layer in order to ma chine the rollsurface to the specified. roundness and finish While retaining proper layer thickness.

It is a general object of this invention to provide a new and useful conductor roll of the character described.

It is another object of this invention to provide such a conductor roll which has good electrical and thermal conductivity, good strength and wear characteristics, which is resistant to corrosion and is of sound mechanical design.

Still another object of this invention is to provide a conductor roll having good electrical conductivity to the surface of the roll even though the surface is formed of a heavy layer of corrosion and wear resistant material which would not in itself provide such good conductivity.

Yet another object of this invention is to provide a conductor roll having a replaceable surface layer which is not susceptible of discoloring or marking the stock sheet material being processed in an electrolytic coating system, so that only the surface layer, and not the entire conductor roll, need be replaced after excessive damage to the surface.

Another object of this invention is to provide such a conductor roll which can be reground a number of times for removing surface imperfections and which has increased surface life between each required regrinding operation.

It is also an object to provide a conductor roll according to any of the foregoing objects in which the surface portion is positively locked against movement relative to the remainder of the roll. i

Other objects will be apparent from the following description and the drawings in which:

FIGURE 1 is a perspective view of a form of conductor roll in accordance with the present invention;

FIGURE 2 is an enlarged section along line 22 through the conductor roll of FIGURE 1; and

FIGURE 3 is a section along line 3-3 of FIGURE 2.

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific forms of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the forms or embodiments illustrated.

Turning now to the drawings, there is illustrated a conductor roll which includes an inner shell 12 having a cylindrical outer surface and supported at each end by a trunnion 14. A shaft 16 passes centrally through trunnions 14, coaxial therewith, and is keyed to each of trunnions 14 by a suitable key as shown at 18. The inner shell 12 is strengthened by suitable support plates 20 spaced from shaft 16 and secured to the inner surface of shell 12 to give stiffness to shell 14 without transmitting forces through the support plates.

An outer shell 22 is provided in the form of a machined centrifugally-cast tubular member surrounding and tightly contracted against the outer surface of inner shell 12 so that outer shell 22 is securely held as an outer layer against inner shell 12. A pair of corrosion-resistant end caps 24, e.g., of neoprene (polychloroprene) rubber or the like, cover the portions of trunnions 14 and the otherwise exposed ends of inner shell 12 which would otherwise come into contact with corrosive acids in the plating bath during use of the conductor roll.

The conductor roll illustrated is water cooled during its use and is therefore provided with water passages in the form of bores 26 in shaft 16 for flowing water through the hollow interior of inner shell 12. Plates 20 are provided with passages indicated at 28 permitting free flow of water throughout the shell interior, and a corrosion resistant coating 30 is applied to the inner surfaces of the inner shell 12 and trunnions 14.

The illustrated conductor roll can be mounted by suitable bearings, e.g., as indicated at 32, supported in walls of a cleaning or plating tank in an electrolytic coating system, or in any other normal manner for mounting a conductor roll.

The inner shell 12 is formed of a highly electrically conductive metal such as an allow of aluminum and copper. The shell can be formed by shaping and welding a plate in tubular shape or can be cast or formed in any other manner. Preferably, the metal of the inner shell includes about 13 to 88 weight percent copper and about 9 to 85 weight percent aluminum. Compositions of suitable alloys are as follows:

ALLOY NO. 1

Element: Weight percent Aluminum 9 to Iron, maximum 1.5 Copper 88 Others .60

ALLOY NO. 2

Element: Weight percent Aluminum 84 to 86 Iron, maximum 1.5 Copper 13 Others .60

ALLOY NO. 3

Element: Weight percent Aluminum 17 to 18 Iron, maximum 1.5 Copper 80 Others .60

Of the above, the alloys numbers 2 and 3 are preferred because of their lesser expense. Where high current carrying capacity is required, alloys having higher copper contents, and even copper alone, would be used.

The outer shell 22, it will be noted, is a seamless shell and is advantageously formed by centrifugally casting, a procedure well known in the art. Briefly, during centrifugal casting, a permanent metal mold is spun in a horizontal position while molten metal to be used in forming the shell 22 is poured into the mold. The mold is of the 4 correct size to provide the desired diameter of the seamless shell 22. The metal solidifies in the mold in the form of the shell and the shell is removed from the mold. The shell is then rough machined and heat treated to the desired hardness, e.g., to Brinell, for maximum corrusion and abrasion resistance.

The shell 22 is then assembled over the inner shell 12. Accordingly, the shell 22 is bored concentric at a close tolerance, e.g., .015 inch, slightly smaller than the diameter of the outer surface of shell 12. The shell 22 is then heated, e.g., to about 500% F, to expand the shell, e.g., about .025 to .030 inch, to an inner diameter, larger than the outer diameter of shell 12, whereupon the shell is slipped over the inner shell and permitted to cool, providing an interference lit to the inner shell, e.g., or" about .018 to .022 inch. The trunnions 14 and shaft 16 can then be placed in position with trunnions 14 being welded to the inner surface of shell 12. During heating of the outer shell to expand, care should be taken not to heat to a temperature sufficient to destroy its desirable hardness properties. However, should such temperature be exceeded, it is only necessary to reheat the shell to a highly elevated temperature followed by a period of controlled temperature reduction until the shell regains its properties.

The preferred metal for the outer shell 22 is one which possesses excellent corrosion and Wear resistant properties and is still sumciently conductive so that, when backed tightly by the more highly conductive inner shell 12 over the entire interior surface of the outer shell 22, suflicient passage of electrical current is permitted through shell 22 to the outer surface to carry out a normal plating operation using a low voltage power source at a high current density. One particularly preferred stainless steel alloy having such properties has the following non-ferrous chemical analysis:

CHEMICAL ANALYSIS (ELECTROLOY #9205) Columbian addition 8 times the target for carbon hardness 130 to 140 Brinell.

The trunnions 14 are of a highly electrically conductive material, as in inner shell 12, such as any of the aluminum and copper alloys numbers 1 through 3 listed above. Shaft 16 can be of hot-rolled carbon steel, heat treated to 90,000 pounds minimum yield, giving excellent strength to the shaft. It will be noted that the shaft 16 is in electrical contact by its force-fit with trunnions 14- over a very large surface area giving sufiicient electrical contact to carry a 10 to 30 volt, 10,000 to 25,000 amp load, e.g., as may be needed when fused electroplating tin is used in lieu of a solution bath.

The conductor roll can also be provided with means for preventing relative movement of the outer and inner shells so that the outer and inner shells will rotate together with the conductor roll shaft. Such means preferably are positive holding means such as pins, welds or the like and also also preferably electrically conductive. Referring to FIGURES 2 and 3, a plurality of electrically conductive pins 41 are provided in bores extending from the outer surface of outer shell 22 into the inner shell 12 for securing the outer shell against movement relative to the inner shell. To include such pins in the structure, the outer shell. 22 is assembled on inner shell 12 as described above. The structure is then drilled from the outer surface of outer shell 22 into the drum or shell 12 and tapped to receive the threaded pins 41. In the form shown, three pins were used at each end of the conductor roll equally spaced around the conductor roll.

The present conductor roll structure is suitable as a replacement for carbon rolls and can be manufactured at as little as one-quarter to one-third the cost of the cast carbon rolls now in use. The present rolls are comparative.y long lived and have markedly better wear characteristics. Also, the present conductor roll structure does not require niclrel and/ or chromium coatings on the exterior surface, which may have to be intermittently stripped and replaced as the conductor roll becomes Wom. Rather, the outer shell is of a corrosion resistant and wear resistant material; it is only necessary to regrind the surface when it becomes unduly worn, and it has been found that a /8 inch thick outer shell can be reground three or four times before the outer shell needs replacing. Replacement can be effected by stripping the old outer shell from the inner shell, heating a new outer shell to expand and permitting the new outer shell to contact over the inner shell as described above. In normal use, the inner shell should never need replacement due to corrosion.

It has further been found that the present conductor roll has a roll life as much as four times that of a copper roll. Thus, four times as much material can be processed before regriuding of the roll is required. The longer roll life results in less down time and lower roll inventories.

Also, the cost of manufacture of the present roll is less when compared to the cost of manufacture of a rolled and welded sheet applied to an inner shell, especially due to savings in materials used in the outer shell layer. In the rolled and welded sheet structure, it has been found necessary to use a one-inch plate to give a three-eighths inch layer after finishing, involving a cost about three times that of the seamless centri-cast layer.

We claim:

1. A conductor roll for use as an electrode in a bath of an electrolytic coating or cleaning system, which comprises a shaft, an inner, highly electrically conductive, tubular metal shell, a highly electrically conductive metal trunnion means supporting said inner shell on said shaft for rotation therewith, and a seamless, outer, centrifugally cast, electrically conductive tubular metal shell contraction fitted on said inner shell in compression force-fit with and covering the outer surface of said inner shell providing electrical connection between the inner and outer shells, the metal of said outer shell being highly resistant to acid corrosion and having lower electrical conductivity than the metal of said inner shell.

2. The conductor roll of claim 1 wherein the metal of said outer shell comprises chromium-nickel stainless steel.

3. The conductor roll of claim 1 wherein the metal of said inner shell comprises aluminum and copper.

4. The conductor roll of claim 1 including positive securing means securing said outer shell against rotation relative to said inner shell.

5. The conductor roll of claim 1 wherein the metal of said inner shell comprises an alloy of 13 to 88 weight percent copper and 9 to 85 weight percent aluminum and contains no more than 1.5 percent iron.

6. The conductor roll of claim 1 wherein said shaft is steel.

7. The conductor roll of claim 1 wherein the metal of said trunnion means comprises an alloy of aluminum and copper.

8. The conductor roll of claim 1 wherein the metal of said outer shell comprises stainless steel having the fol lowing non-ferrous analysis:

Element: Percent by weight Carbon, maximum .03 Chromium 19.0-22.0

Columbian addition 8 times the target for carbon hardeners to Brinell.

9. The conductor roll of claim 8 wherein the metal of said inner shell comprises:

Element: Parts by weight Aluminum 9 to 10 Copper 88 Iron, maximum 1.5

10. The conductor roll of claim 8 wherein the metal of said inner shell comprises:

Element: Parts by weight Aluminum 84 to 86 Copper 13 Iron, maximum 1.5

11. A conductor roll for use as an electrode in a bath of an electrolytic coating or cleaning system, which comprises a steel shaft, a first tubular metal shell formed of electrically conductive metal, electrically conductive metal trunnion means of the same metal as said first shell secured to and supporting said first shell on said shaft for rotation therewith, a seamless second tubular metal shell centrifugally cast of electrically conductive metal and having a normal inner diameter smaller than the outer diameter of said first shell but sufficiently close to the outer diameter of said first shell for thermal expansion of said posed closely covering the outer surface of said first Shell and surrounding said first shell while said second shell is in an expanded heated state relative to said first shell and being contraction fitted by cooling from the expanded heated state against the outer surface of said first shell in tight contact therewith maintaining complete electrical contact between the first and second shells, the metal of said second shell being highly corrosion resistant to the bath and having lower electrical conductivity than the metal of said first shell, and electrically insulating means covering the portion of said trunnion means and ends of said inner shell exposed to the plating bath.

12. The conductor roll of claim 11 wherein said insulating means is a layer of polychloroprene rubber.

13. A conductor roll which comprises an inner electrically conductive tubular metal shell, means supporting said inner shell for rotation about its axis, an outer severable electrically conductive tubular metal shell in tight surface-to-su'rface fit on said inner shell for providing electrical connection between the inner and outer shells, and means securing said outer shell for rotation with said inner shell.

14. The conductor roll of claim 13 wherein said secur- 'lng means is electrically conductive.

References Cited UNITED STATES PATENTS 1,403,257 1/1922 Lewis 29-447 2,095,719 10/1937 Sinclair 29447 2,958,742 11/1960 Palmer 204-279 XR 3,014,266 12/1961 Samuels 29-447 3,047,478 7/ 1962 Marsh et al 204107 XR HOWARD S. WILLIAMS, Primary Examiner.

D. D. JORDAN, Assistant Examiner.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3,374,165 March 19, 1968 John W. O'Brien et al It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, lines 47 and 48, cancel "Columbian addition 8 times the target for carbon hardeness 130 to 140 Brinell" and insert Columbium addition 8 times the carbon precent for target hardness of 130 to 140 Brinell Column 6, lines 8 and 9, "cancel "Columbian addition 8 times the target for carbon hardeners 130 to 140 Brinell" and insert Columbium addition 8 times the carbon percent for target hardness of 130 to 140 Brinell line 34, after "said", second occurrence, insert second shell to an inner diameter greater than the outer diameter of said first shell, said second shell being dis- Signed and sealed this 23rd day of December 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents

Claims (1)

1. A CONDUCTOR ROLL FOR USE AS AN ELECTRODE IN A BATH OF AN ELECTROLYTIC COATING OR CLEANING SYSTEM, WHICH COMPRISES A SHAFT, AN INNER, HIGHLY ELECTRICALLY CONDUCTIVE, TUBULAR METAL SHELL, A HIGHLY ELECTRICALLY CONDUCTIVE METAL TRUNNION MEANS SUPPORTING SAID INNER SHELL ON SAID SHAFT FOR ROTATION THEREWITH, AND A SEAMLESS, OUTER, CENTRIFUGALLY CAST, ELECTRICALLY CONDUCTIVE TUBULAR METAL SHELL CONTRACTION FITTED ON SAID INNER SHELL IN COMPRESSION FORCE-FIT WITH AND COVERING THE OUTER SURFACE OF SAID INNER SHELL PROVIDING ELECTRICAL CONNECTION BETWEEN THE INNER AND OUTER SHELLS, THE METAL OF SAID OUTER SHELL BEING HIGHLY RESISTANT TO ACID CORROSION AND HAVING LOWER ELECTRICAL CONDUCTIVITY THAN THE METAL OF SAID INNER SHELL.

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