US2429902A - Apparatus for producing electroplated sheets - Google Patents

Description

Oct. 28, 1947. M STERNFELS 2,429,902

APPARATUS FOR PRODUQING'ELECTROPLATED SHEETS Filed Jan. 15, 1943 2 SheetsSheet l QM lam/km.-

7 Oct. 28, 1947; M. M. STERNFELS APPARATUS FOR PRODUCING ELECTROPLATED SHEETS Filed Jan. 15, 1943 2 Sheets-Sheet 2 Patented Oct. 28, 1947 APPARATUS FOR PRODUCING ELECTRO- PLATED SHEETS Martin Misternfels, Waterbury, Conn, assignor to hro m p r n of America, :N w York, N. Y, a-corporation of Delaware Application January 15, 1943, Serial No. 472,504

1 Claim.

This-invention relates to apparatus for producing electroplated sheets; andit comprises a method wherein a suitable metal is deposited from an electrolytic plating bath on the cylindrical surface of a rotating metal drum, having insulated ends and a cylindrical conducting face, between at least. two endless, flexible insulating masking-tapes, which are wound thereon and two of which may cover the joint between the insulated ends and the conducting face of the drum, the resulting metal deposit being usually continuously stripped from the drum as plating progresses and said masking tapes being separated from the surface of the drum either simultaneously with or somewhat before the point at which stripping of the metal occurs and bein advantageously cleaned before being re -wound on the plating drum, whereby at least one metal band or sheet is produced having smooth edges which do not require trimming. My invention also includes an apparatus for conducting the described process, said apparatus comprisinga tank containing an electrolytic. metal platin bath, a metal drum, having a cylindrical conducting surface and insulated ends, mounted so that a portion of its surface dips into said bath, means for rotating said drum, at least two-endless insulating masking tapes, means for mountingsaid tapes in such fashion as to cause said tapes to wind and unwind on .said drum while engaging the immersed surface of said drum and covering the joints between the insulated ends nd the eylindricalface of said drum, thereby producing two insulated bands ofdrum surface separated by a conducting-band, means for removing electrolyte from said endless. tapes, means for conveying them back to be re-wound onsaid drum, an anode, means for passing an electric current through said bath from said anode to said conducting band, and means for stripping the deposited metal from said drum; all. as more fully hereinafterset forth and as claimed.

The process of makingmetal foil, wherein a metal is deposited from an electrolytic plating bath on a rotating drum, followed by stripping the metal deposit from =thedrum, has lon been known. However, various difficulties have arisen in the practical operation of this process which have greatly limited its usefulness. Some provision mustbe made to prevent the metal from depositing on the ends of the metal ,drum, since otherwise the metal deposits over these ends and locks itself on. Proposals have beenmade to cover the drum ends withinsulating coatin s .01 discs of insulating material in order to overcome 2. this difficulty. But ithas been found that such provisions are insufficient for the reason that the electrolytic metal invariably deposits inthe joints between the insulatedand the uninsu'lated port ons of the drum inthe form of sprouts. .And this sprout formation produces an irregular con-.

tour at the edges of the foil, while tearing .of the-foil at its edges is of rather frequent occur.-

rence.

Various expedients have been suggested in the attempt to overcome these difficulties. "It has been proposed, for example, to provide an insulating coating extending over the ends of the .drum

and for a short distance over the cylindrical face at both ends. .It has also been proposed to imbed insulating bands of various materialsin the face of the drum at its-ends. Butit hasbeen found thatthe electrolyte always Works its Way under the .edgesofany such insulating. material resultingin thedeposit of metalbeneath suchmatee.

rial. This metal deposit then forms .a base upon which sprout formation takes place.

-I ha-v-e discovered a rather simple expedient which can :be used. successfullyto. overcome the difflcultiesmentioned. I have discovered that, ifinsulating endless. masking tapes are continuouslywound on. and unwound from. the face of the plating .drum, any metal sprouts forming at the edges. or on the faces of the tapes are separated from the drum with the tapes .anddo no further harm. I have found that, if the tapes arecleanedand freed from electrolyte before againbeingwound .on the drum, the penetration of electrolyte and the formation of. a metal depositbeneath the tapes are substantially prevented. I have further found that thesetapes can belused conveniently to cover and protect any insulation provided at the ends of the platingd-rum. .When a drum is used which has insulated ends, these end tapes protect the joint between the insulation and the metal face of the drum, whereby the formation ,of sprouts, and, the deposit of metal is prevented at this joint. The resulting metal foil is then sharp and clean cut at. the edges. procedure I do not attempt to prevent the formation of sprcuts but continuously eliminate any sprouts which are formed before they become of sufficient size to do any harm.

The insulation .provided at the ends of the drum can be either in the form of a coating or in the form of discs or gaskets of insulating material secured to the ends of the drum by suitable means. The end tapes must be sufficient in width to cover the joint between the insulation N0 trimming is required. In this and the metal face of the drum and also to extend over the metal surface for a short distance, say at least about inch. There is no upper limit for the width of the tapes since it is possible, of course, to employ wide tapes extending over substantially the entire surface of the drum, for example if it is desired to produce only a single narrow band of metal foil.

The metals which can be deposited and stripped in the described fashion include copper, zinc, gold, nickel, iron, cobalt and tin. Plating baths of conventional composition can be employed. The drum may be constructed of steel or other suitable metal and it may be chromium plated, if desired, either with or without an intermediate plate of nickel or other metal. It is also possible to plate the drum with lead or tungsten, for example. If insulating discs are employed, these can be constructed of hard rubber, phenol-formaldehyde resins or any of the synthetic plastics which are impervious and resistant to the electrolyte to be employed and which have no tendency to shrink, craze or curl with age. If an insulating coating is employed on the ends of the drum, this may consist of phenol-formaldehyde varnish, rubber cement, cellulose acetate, Vinylite resin or the like. Even a thick coating of wax will give satisfactory results for at least a short time.

The insulating masking tapes to be employed may be constructed of various materials. I have successfully used paper tapes impregnated with a cellulose acetate lacquer and with a phenolformaldehyde lacquer, and cotton tapes impregnated with Vinylite resin. I have also found tapes made from a vinylidene polymer to be satisfactory. The tapes can be made of natural or artificial rubbers or these rubbers can be used as impregnating materials. Any of the flexible, water-resistant synthetic resins or artificial plastics can be .used as impregnants for paper or fabric tapes. And any of these materials, which have sufficient tensile strength to withstand the tension, can be used as such. Impregnated tapes of fabric or textile materials, such as cotton, wool, asbestos or hemp, are somewhat more satisfactory than paper tapes owing to their greater strength. It is only necessary that the tapes employed be impervious and resistant to the electrolyte, sufficiently flexible to cling to the drum surface, strong enough not to break under a tension sufficient to hold them tightly against the drum surface and not thermoplastic at the temperature of operation of the drum.

Various plating expedients can be employed in my process which have been suggested in the prior art. For example, it is possible to circulate the electrolyte through a pump to produce agitation in the plating bath or to introduce air for agitating purposes. Continuous filtration of the plating bath can be used if desired. This eliminates small particles of impurities which might cause holes in the metal foil. If desired the metal surface of the drum may be coated with wax, rosin or other coating materials which have been suggested in the art to prevent too close adherence of the metal deposit to the surface.

If it is desired to produce several bands of metal foil rather than a single wide sheet, this can be accomplished readily by the use of auxiliary insulating tapes intermediate the ends of the drum. These prevent the deposition of metal beneath them and hence bands of metal are produced between the tapes. The intermediate tapes collect and strip off from the drum surface any newly formed sprouts and these can be eliminated by cleaning the tapes before they are re-wound on the drum. It is also possible, within the present invention, to produce electrolytic metal in thick sheets, which is accomplished by rotating the drum and continuing the plating operation without continuous stripping until a coating of the desired thickness is built up. This coating may then be stripped by slitting it transversel and removing it from the drum. Or if it is desired to recover the metal in the form of a cylinder or a :band it can be removed by loosening it from the drum, with the use of heat, if necessary, and then sliding it off one end of the drum. It is evident that circular bands or rings of metal can be produced in the same fashion provided that intermediate insulating tapes are used. These tapes operate continuously during the plating operation preventing the formation of sprouts and producing smooth, clean cut edges on the plated metal.

My invention can be explained in greater detail by reference to the accompanying drawing which shows. more or less diagrammatically, an apparatus within the scope of my invention and useful in conducting my process. In this showing;

Fig. 1 is a plan view of a plating tank with plating drum and accessories necessary for the manufacture of metal foil in strips,

Fig. 2 is a vertical section through the plating tank, taken along the line 2-2 of Fig. 1, showing one end of the plating drum in elevation, part of the insulating disc of the drum being broken away to show details,

Fig. 3 is a partial vertical sectional view through the plating drum and anode, taken along the line 3-3 of Fig. 2 and at right angles to the showing of Fig. 2, while Fig. 4 is a similar showing of a modification.

In the various figures likes parts are designated by like reference numerals. The plating tank shown at I3 is filled with an electrolyte l2. The plating drum [0 is supported in this tank by means of shaft l1 mounted in bearings, not shown, in such fashion that its lower surface dips beneath the electrolyte. An anode M is also mounted in the tank, being supported from anode bars I5 and being bent in such fashion that it closely conforms with the contour of the immersed face of the plating drum but being spaced therefrom. This anode may be of the soluble or insoluble type as will be understood by those skilled in the art, and it may be enclosed in a bag, if desired. The surface of the drum forms the cathode, electrical connection being made therewith by means of the brush 9 and the lead 1, while current is supplied to the anode by means of the leads 8. During the plating operation the drum is rotated by means not shown in the direction of the arrow shown in Fig. 2 and the metal deposits on the face of the drum, wherever it is exposed to the electrolyte, in the form of on or more sheets or bands ll. These sheets or bands are usually continuously stripped off the face of have their inner peripheral edges cut away, as at 21, in Fig. 3, leaving outer peripheral flanges 26 which extend beyond the face of the metal drum forming shoulders whose faces 28 are flush'with the face 29 of the drum. The joints between these flush faces are protected from the electrolyte by means of flexible insulating tapes I!) which form an important feature of this invention. These tapes are endless and run over spools 20 and 20', mounted on shafts 2!. The spools are prevented from moving endwise along their shafts by means of collars 22. These means accurately guide and support the tapes in such fashion that they firmly contact the face of the drum in strips where it dips beneath the surface of the electrolyte. Intermediate tapes I9, mounted in the same manner and contacting the metal face of the drum, can be employed, if it is desired to produce the foil in bands rather than in a single sheet.

The insulating tapes are advantageously washed or otherwise cleaned, to remove electro-' lyte and any bits of metal which may have deposited on them, by passing them through a cleansing liquor in container'M. The liquor may be an acid, if that is found necessary, but water is usually satisfactory to provide adequate cleansing. The tapes are held beneath the surface of the cleansing liquor by means of the roller 23 which is mounted in suitable bearings 34 provided in the ends of the tank. The tapes can be tensioned individually by conventional means not shown. After the tapes are cleansed they are led back beneath the tank, as shown in Fig. 2, to the spools 20 from which point they are again contacted with the drum before the drum surface reaches the electrolyte. It is desirable to have the tapes substantially free from electrolyte when they contact the drum in order to prevent a film of electrolyte from being present beneath the tapes. This substantially prevents the deposit of metal'beneath the tapes and hinders the formation of metal sprouts at the edges of the tapes.

It will be noted that in Fig. 2 the metal foil is stripped from the drum surface at a point 35 which is above the point 36 at which the tapes are separated from the drum surface, that is, the tapes are separated from the drum surface prior to the separation of the metal foil from the drum surface. It is important in the production of smooth edges on the foil that the tapes be separated from the drum surface at least not later than the separation of the metal foil from the surface. This eliminates the danger that any metal deposited beneath the tape might cause the foil to tear at its edges.

The drum shown in Fig, 4 differ from that of Fig. 3 in that the insulating discs at the ends of the drum are replaced by insulating coatings 3| which extend to a point where they are flush with the face of the drum. When insulating end coatings of this type are employed, the tapes I 9 should cover the joints between the metal and insulation and they advantageously extend over the peripheral edges of the coatings. There is always a tendency for the electrolyte to gradually work beneath the edge of an insulating coating and, when the insulating tape covers this edge, this tendency is minimized.

In order to reduce the tendency for the formation of an excessive deposit of metal at the edges of the foil, the anode should either be bent backwardly away from the drum at its edges, as shown at 33 in Fig. 4, or should have a width which i somewhat less than the length of the of foil can therefore be produced with a single drum. If it is desired to produce only a single rather narrow sheet of foil, it is only necessary topmploy Wide end tapes which cover the portions of the drum on which a deposit of metal is not desired. Or the two intermediate tapes shown in Fig. 1 can be used alone. This leaves an inner strip of the required width and the metal deposited within this strip can be stripped off the drum while that deposited on the rest of the drum may be left to accumulate, being later recovered as scrap. Another expedient is to use two intermediate insulating tapes While applying an insulating coating on the face of the drum on either side of the tapes. Since the insulating tapes can be ied 0n the drum with extreme accuracyfrom the spools 20' it is possible to make accurately dimensioned sheets or strips of foil. As mentioned previously it is also possible to make thick sheets or rings or cylinders of electrolytic metal by use of my process. It is therefore evident that my method and apparatus are extremely flexible.

While I have described what I consider to be the most important embodiments of my process and apparatus it is evident that various modifications may be made in the specific procedures and devices which have been disclosed without departing from the purview of this invention. The rate of rotation of the plating drum can be varied widely, depending upon the thickness of the foil desired, the plating current, the composition of the plating bath, the circumference of the drum, etc. When a high current density is employed and the drum has a large diameter, it may be rotated rather rapidly in the production of a thin foil. And if stripping is not continuous, that is, if it is desired to produce a ring of metal rather than a foil, rapid rotation is of advantage in the production of a smooth deposit. The dimensions and the construction of the plating bath and drum to be used in my process can be varied widely. The materials from which these elements are constructed may also be varied. For example, it is possible to construct the plating tank of wood or ceramic materials, or it may be of iron coated with lead, the lead coating being used as anode, if desired. The drum may be constructed of wood or ceramic materials also, if a cylindrical metal face is provided. The various materials from which my insulating tapes and drum ends can be constructed have already been listed. And a description has already been given as to how my process can be varied to produce thick plates, rings or cylinders of metal, as well as metal foil in sheets or strips. While I have listed several metals from which these articles can be produced in accordance with my invention, it is also possibleto produce in a similar manner articles of non-metallic materials which can be plated out electrolytically. Thus various rubbers and artificial resins can be plated on a rotating drum'anode between endless tapes, the deposit being either stripped continuously or al- 7 lowed to accumulate to produce rings or cylinders, for example. Other modifications of this invention which fall within the scope of the following claim will be immediately evident to those skilled in this art. 7

What I claim is:

An apparatus for producing electrolytic metal foil which comprises a tank containing a metal plating bath, a metal drum having a cylindrical, electrically-conducting surface with insulated ends substantially flush with said conducting surface mounted so that a portion of its surface dips into said bath, means for rotating said drum, at least two endles insulating masking tapes spaced parallel and mounted in such fashion as to wind onto and unwind from said drum while engaging the immersed surface of said drum and covering the joints between the insulated ends and the conducting surface of the drum, thereby forming two insulated bands of drum surface separated by a conducting band, an anode, means for passing an electric plating current through said bath from said anode to said conducting band serving as cathode, whereby a deposit of electrolytic metal forms on said conducting band, means for continuously stripping said electrolytic deposit from said drum, means REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA IiaN TS Number Name Date 1,425,184 Edison Aug. 8, 1922 1,600,257 Topping Sept. 21, 1926 1,731,415 Grupe Oct. 15, 1929 2,044,415 Yates June 16, 1936 2,051,928 Yates Aug. 25, 1936 1,416,692 Dantsizen May 23, 1922 FOREIGN PATENTS Number Country Date 119,031 Austria Sept. 25, 1930 465,821 Great Britain 1937

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