US2490055A - Metal strip electroplating apparatus - Google Patents

Description

Dec. 6, 1949 c. M. HOFF METAL STRIP ELECTROPLATING APPARATUS Filed March 50, 1944 2 Sheets-Sheet 1 INVENYOR.

Patented Dec. 6, 1949 UNITED STATES PATENT OFFICE METAL sum ELrfif'izoPLirriNG *APPARA US lay qn Heft, Wi gt n, el-i..'a r, b

mesne assignments,

to v lfilational *Steel Corpor'atio'n, a corporation Beware Application Mar'chco, 194-4, seriall 5285673 3 Claims.

1 a This invention relates to an apparatus for the application of electrodeposits to metal strips and is more particularly directed to electroplating apparatus for the high speed plating of strip me tal using readily oxidized plating solutions wherein excessive aeration of solution is avoided. M It is an object of the present invention to pro; v id e "apparatus well adapted for the handling ,gf stannous tin plating solutions. It is 'a furthat object to provide apparatus for handling fm etaI strip at high speed and effecting contact "between a plating solution and the strip with ut excessive aeration of the solution. It is 'a still firmer object to provide apparatus which does n'ot involve a radical departure from existing equipment so that such existing equipment can ""adily be altered to conform to the pres ntintion. Still further objects will become apparent hereinafter. v

The foregoing and other objects of the invention are attained by the use'of an apparatus more particularly described hereinafter and 'illustrated in the accompanying drawings in Wljichz I A Figure l is a semi-diagrammatic showing'of "an assembly of a typical plating unit of the resent invention, I Figure 2 is a cross section illustrating a modified apparatus of the invention, and a x t Figure 3 illustrates a still further modification 'jif a roll'assembly where the solution level is maintained above the strip'being plated. I In the general assembly of Figure 1 there will be seen a plating receptacle, I, which is conjfstructed of a suitable material or is suitably lined fto resist corrosion by the plating solution "empl oyed. For a stannous chloride-sodium fluoride bath of a pH about 3 there would be useZLjfor sesame, a tank lined or coated with rubben'poly chloroprene or polyvinyl chloride. a 7 The plating tank, I, is provided with supports, gffo r'holding anodes, 3, in a suitable spaced rela- "em; to the strip to be plated. The anode supports, 2, are made of a suitable conducton suc'h 'carbon, while'the anodes are preferably made "6f ft he'metal to be plated, for instance, tin.

fAtthe entrance end of the platin'gtank th'e're areprovided rolls, 4 and 5. At the exit endthere afr e provided rolls, 6 and 1. The pairs 'o'fffrolls, 'I 5 and 6 -1, engage the strip of metal, Bftdbe '2 plated andserve as guide rolls in the passage of stripacross the top-of theplating tank. Driving arolls, ;not shown, engage the :strip and pull it thrp. the plating equipment. The rolls, 45 and Ii- 1, are driven, by means not shown, so that they turn in synchronism with the driving rolls, but the drive is not positive so thatrolls 45 and 6'--'I may slip to stay-at thesame speed as the moving strip, In this way the rolls shown are "10 driven so that they do not depend upon friction with the strip to turn them, but they are not so posiitively driven that they will go at a different speed from the strip and scratch it. The upper rolls i and 6 are metal and some or all of these uppe r'rolls may serve as electrical contacts. The 10 r rolls 5 and I are back-up rolls and are pr erably made of a nonconducting material "suchas rubber.

sides of the tank, I, are preferably somewhatraisdto minimize overflow of solution. At each end'of the tank there is provided means for retaining solution. As shown at the entrance end of the'tank, there is a sealing means or wall, l9,' e' i'teii'dingfrom the'bottoinof the tank towards the lowerfroll, 5. The upper end of the member 9 terminates in a resilient wiper, II]. The wiper, III, may suitably'be made of rubber. It will be is' 'een "that the solution will be prevented from flowing out of the tank by the wall, 9, the wiper, ID, the roll, '5, and,'of course, by the extension,

'I I, ofthe sides of the tank, I. identical construction 'r'nay be used at the exit end 'of the tank, but for "purposes of illustration; there is' showna very similar construction "which has 'proven successful in plant practice. A."retaining member, I'2,'extends from the end of the l4,and is provided with a rubber wiper, "I3. Itwill'be'obs'erv'ed that the wall, I4, serves to restrain the unimpeded flow of solution and it 40 alsoserves as an electrical shield to minimize plating on the roll. This structure and the wall, I 4, 'are'very important when the strip is moving *at'hig'hspeed. Without means for retaining the solution it would be carried out of the tank so fast redeem ng-would be impossible.

'o'lution which passes through the rolls or 'hich'splashes over the sides of the plating re- :ceptfacle is caught in the tray, I5. Solution from trayis withdrawn from the tray through a "hire, '16, to a tank, '11, frorn'which itis returned by a pump, l'8, to the plating tank, I, by the pipes, I9 and 20.

In the operation of the apparatus illustrated in Figure 1, any suitable solution such as a stannous chloride-sodium fluoride tin plating bath is put in the tank, I. A metal strip, such as strip steel, is run across the top of the receptacle, the solution level being such that at least the lower surface of the steel is in contact with the electrolyte. Suitable anodes, such as tin are slipped into place and electrodeposition is effected in the customary way by the application of current.

The strip steel is guided as it moves rapidly across the top of the cell by the rolls, 45 and 6-'l. caught and returned to the tank. It will be seen that only a relatively small amount of the solu-.

tion will overflow, and thus aeration will be held at a minimum. It will also be understood that the assembly of Figure 1 represents only a single plating unit and a number of such units will ordinarily be required to obtain a suificiently heavy metal deposit at relatively high speeds.

In Figure 2 there is illustrated a modification in which two units like that of Figure 1 are juxtaposed. The plating tank, I, is provided with a retaining member, 9, and a Wiper, N), at the inlet and at the exit end. The construction in eiiect provides two tanks, like that in Figure l, which are joined by a member, 2!, which extends around the bottom and sides of the tank to form one long plating tank. Rolls 22 and 23 are pro vided intermediate the length of the long tank to provide driving power, to hold the sheet in position, and to provide an electrical contact. Walls, 2t and 25, serve to minimize plating on the roll 22 and to slow down the motion of plating soiution.

It will be seen that the modification of Figure 2 is applicable to installations using a still larger number of tanks. Thus, according to the invention, one may either use a plurality of elements like that shown in Fi ure 1 or may use a plurality of elements joined by rolls, such as 2223, the tanks in the latter event being interconnected.

Figure 3 illustrates a still further modification and shows the exit end of a modified structure. tank, l, is provided with a wall, 9, and a Wiper, it There is also provided a wall, It, which serves like that of Figure 1.

The apparatus of Figure 3 is characterized by the fact that the sides of the tank are considerably than those of Figure 1 so that the solution level may be raised to a point well above the moving strip and the strip accordingly may be plated on both sides at the same time. Anodes, 26, may be provided for this purpose. It is to be noted that the anodes, 25, may be omitted and this structure used if it is considered important to maintain a somewhat higher solution level than that readily obtainable in a structure of Figure l. I

A suitable solution retaining member, 2?, is provided and this carries at its end a wiper, 28. It will be seen that this structure minimizes the loss of solution at the exit end of the plating receptacle as shown.

While I have shown certain illustrative embodiments of the invention, it will be understood that one skilled in the art may without depart.- ing from the spirit of the invention readily devise numerous similar apparatus for the plating of strip metals with a minimum of solution aeration.

Any solution which overflows will be I claim:

1. A strip plating apparatus comprising a tank for holding a plating solution, having side, end, and bottom walls, means for passing a strip across the top of said tank in a plane substantialiy coincident with the plane of solution level, said last-mentioned means comprising a lower roll at the exit end and located with its upper surface substantially tangential to the plane of the solution level, and a cathode contact roll above said roll, said rolls being adapted to re ceive the strip therebetween, the end wall of said tank at the exit end extending upward almost to the plane of the solution level and being positioned so that the rolls are beyond the said end wall in the direction of motion of said strip, an anode located in said tank below the solution level, electrode connections for the said anode and for said contact roll, extensions on the side walls of the tank and a sealing means extending from the said exit end wall to said lower roll which together with the extensions on the side walls of the tank form a container for holding the plating solution and for restraining its fiow from the tank.

2. A strip plating apparatus comprising a tank for holding a plating solution, having side, end, and bottom walls, means for passing a strip across the top of said tank from end to end in a plane substantially coincident with the plane of solution level, said last-mentioned means comprising a lower roll located at the exit end with its upper surface substantially tangential to the plane of the solution level, and a cathode contact roll above said lower roll, said rolls being adapted to receive the strip therebetween, the end wail of said tank at the exit end extending upwardly almost to the plane of the strip and being positioned so that the rolls are beyond the said end wall in the direction of motion of said strip, an anode located in said tank below the solution level, electrode connection for the said anode and for said contact roll, side wall extensions extending from the side walls to the rolls and above the plane of the strip, and a sealing means extending from the said exit end wall to said lower roll, said sealing means and said rolls together with the extensions of the tank side walls forming a container for holding the plating solution and for restraining its flow from the exit end of the tank.

3. A strip plating apparatus comprising a tank for holding a plating solution, having side, end, and bottom walls, the side walls extending above the solution level, means for passing a strip across the top of said tank from end to end in a plane substantially coincident with the plane of solution level, said last-m ntioned means comprising a lower roll located at the exit end with its upper surface substantially tangential to the plane of the solution level, and a cathode contact roll above said lower roll, said rolls being adapted to receive the strip therebetween, the end wall of said tank at the exit end extending upwardly almost to the plane of the strip and being positioned so that the rolls are beyond the said end wall in the direction of motion of said strip, an anode located in said tank below the solution level, electrode connection for the said anode and for said contact roll, side wall extensions extending from the side walls to the rolls and above the plane of the strip, and a sealing means extending from the said exit end wall to said lower roll, said sealing means and said rolls together with the extensions of the tank side walls forming a con- 5 6 tainer for holding the plating solution and for re- Number Name Date straining its flow from the exit end of the tank. 2,240,265 Nachtman Apr. 29, 1941 CLAYTON M. HOFF. 2,244,423 Hall June 3, 1941 2,324,652 Stoker July 20, 1943 REFERENCES CITED 5 2,377,550 Hall June 5, 1945 The following references are of record in the 2334560 Ward sept- 1945 file of this patent: FOREIGN PATENTS UNITED STATES PATENTS Number c t y t Number Name Date 10 467,019 Great Britain June 9, 1937 347,959 Rau Aug. 24, 1386 OTHER REFERENCES 929,312 King July 27, 1909 1 9 3 Battle July 13 191 Metal Finishing, February 1 4, pages '77 to 1,813,297 Klein July 7, 1931 '79, article entitled Electrotinning Steel Strip at 2,061,554 Billiter Nov. 24, 1936 u Weirmn steel 2,223,860 Schellenberg D86. 3. 1940

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