US1768358A - Electrolytic process and apparatus - Google Patents

Description

June '24, I

H. c HARRiSON ELECTROLYTIC PROCESS AND APPARATUS Filed May 21, 192 5 IN Vli/YTOR A TTOR NE m.

2Sheets-Sheet 1 June 24, 1930. H. c. HARRISON ELECTROLYTIC PROCESS AND APPARATUS Filed May 21, 1925 2 Sheets-Sheet 2 INVENTOR A TTORNE VJ Patented June 24, 1930 UNETE STATES HERBERT CHAMPION HARRISONMOF. LOGKPQRT, EW YORK; FLoRENois ivrnannrson,

ARTHUR B. B. nanmson. AND wILLiAM W. "oa vrrnnrm, xEo 'roRsfoF'fsAID"finn- BERT CHAMPION HARRISON, DECEASED v ELECTROLYTIC raoonss [LAND Am nArrus Application filed May 21,

This invention relates to a process and apparatus for electrolytically depositing metals, such as copper, of good physical quality, at 'a rate of speed hitherto deemed 6 impracticable commercially.

Ithas beenfwell recognized for at least twenty-five years, that in order to obtain a coherent deposit ofcopper or other metal of good quality upon a cathode surface in an 10 elQlztrolytic cell, it is necessary to maintain the concentration of the layer of electrolyte immediately in contact with the cathode, so that impoverishment of the electrolyte does not occur, since agivencurrent of electricity flowing for a given time always deposits the same amount of a given element from an electrolyte, providing the layer of electrolyte next to" the cathode is not impoverished.

For thepurpose of obtaining rapid deposition upon the cathode it is, therefore, necessary to utilize high current densities and to renew the concentration of the electrolyte with a rapidity to accord with the current density. Unless concentration of the electrolyte is maintained, high current densities are ineffective to deposit pure coherent metal on the cathode.

The history of the art of electro-deposition shows that relativelyhigh-rate copper deposition hasbeen possible for many years, although accompanied by physical limitations that have impeded commercial production while not inhibiting it, altogether.

i In the prior art, in so far as I am aware, the cathode. and anode containing portions of the cell have been so related that the electrolyte can pass freely from one portion to the other, both portions open to the atmosphere and both under atmospheric pressure. In cells of this character both cathode and anode compartments being open to atmosphere, it is not practicable to effect rates of circulation required to utilize successfully current densities much in excess of 200' amperes per square foot.

I believe that I have solved the problem of utilizing extremely high current densities, by injecting into the art a new principle. In the process of this application, the cathode is completely separated from the anode or 1925. Serial No. 31 ,922.

anodes by, and is enclosed in, a tunnel like chamber open only at opposite ends for the admission andescape of electrolyte and for the passage of, the cathode,which may be' a moving ribbon of indefinite length. The wall of this cathode-enclosing chamber is of porous, non-conducting material, permeable tothe electric current when'-saturated"witli electrolyte, which acts as the conducting medium between the anode and the cathode. The chamber serves as an efficient guide. to direct a stream of electrolyte in contact with the entire surface of the cathode, While at the same time serving to allowa small predetermined proportion of the electrolyte, v

say ten per cent, to passjthrough and form a second streamof lower velocity, flowing through the anode compartment or compartments. This tunnel-like cathode compartment-should conform in cross section to the sure dropping on the passageof the electrolyte through the compartment only slightly when once the speed of the streamis'attained. At the same time, the porosity of the inclosing wall acts as a pressure reducing valve, allowing the small proportion of the electrolyte required to percolate through it into the anode compartmentor compartments, which is or are at atmospheric or at least lower pressure, than the cathode chamber and in which the rate of flow is much reduced.

It is possible by this mode of procedure to, effect satisfactory deposition of copper, for example, at'rates as high as 2,000 amperes to the square foot, although it is obvious that with such high rates the voltagev practice the process described;

Fig. 2 is a cross section of the electrolytic cell forming a part of the apparatus, taken on the line 2-2 of Fig. 1;

. Fig. 3 is a cross section on the line 3-3 of Fig. 1;

Fig. 4 is a cross section on the line 44 of Fig. 1;

Fig. 5 is a plan view, partly in section, of the apparatus, but without the elevated tank for affording a pressure head for the electrolyte; the pump delivery pipe to said reservoir, and the stand pipe leading therefrom being shown in section.

. Fig. 6 is a section on the line 66 of Fig. 5, looking to the left;

Fig. 7 is a cross section of a fragment of the tunnel-like cathode compartment, of about full width; and Fig. 8 is a longitudinal section through a fragment of the cathode compartment.

The apparatus here exempli ed in Figs. 1 and 5 as one that is suitable to practice the process disclosed consists of the following main elements, namely: An electrolytic cell proper, 10, with certain directly connected appurtenances; a drip pan or catch tank 11 to receive the electrolyte discharged from the cell; an elevated reservoir 12 to hold a head of electrolyte; a pump 13 with intake pipe 14 leading from the catch pan 11 and discharge pipe 15 delivering to the elevated reservoir 12; a stand-pipe 16 adapted to deliver the electrolyte from the reservoir 12 into and through the cell with high velocity; a delivery spool or reel 17 for receiving a roll of ribbon-like cathode of indefinite length, and a power-driven reel 18, to wind up the compound strip comprising the cathode ribbon and adhering layers of deposited metal, and draw the cathode strip at any predetermined rate of speed through the cell.

The cell 10, as well as other parts that come in contact with the electrolyte, may be constructed of any suitable acid-proof material known for the purpose. The walls of the cellmay be made, for example, of wood, lined with lead, of soapstone, acidproof brick or tile, glass or vulcanite; and certain attachments, subject to contact with the electrolyte, may be made of any of the materials mentioned or any other suitable I substance. The cell proper, 10, is confined within the side walls 19, front end wall 20, rear end wall 21, and bottom 22, of an elongated box. The front end wall 20 and the rear end wall 21 are slotted vertically. The slot in the rear wall 21 is indicated at 23 in Fig. 3. Both slots are preferably of identical size and form and they are in alignment, preferably in the vertical mid plane of the cell. The slots 23 are for'the purposes of receiving the cathode ribbon 24, permittin its passage through the cell, and allowing t e electrolyte 25 to enter and leave the cell. In dimensions the slots conform closely to the cross sectional dimensions of the cathode ribbon 24, being but very slightly longer than the width of the ribbon and of a width to allow not more than about onesixteenth of an inch space on each side of the ribbon. The ribbon may be of standard rolled stock, eight inches in width, five one-thousandths of an inch in thickness, and of indefinite length. These dimensions have been found suitable for my purposes, but any practicable dimension of cathode ribbon may be used.

Extending longitudinally of the cell in alignment with the slots 23 is a cathode compartment of tunnel-like form 27, completely separated from the anode compartment, which occupies the remainder of:the space within the cell. This tunnel-like cathode compartment is formed as a flat tube, oblong in cross section, the ends of which are seated snugly in grooves 58 in the end walls 20 and 21. The passage or chamber 26 within the tunnel compartment is substantially of the same dimensions in cross section as slots 23. IVithin the passage 26 of compartment 27 there are, preferably, centering guides 28, having V-shaped notches to guide and assist in centering the cathode ribbon within the compartment. These guides may be made of agate or other hard, acid-proof substance. In order to avoid, by any peculiar mischance, contact between the sides of the ribbon cathode and the walls of the tunnel, other agate or like guides 28 of button-form may be imbedded partially in said walls. There may be three or more guides 28 at the bottom of the passage and an equal number at the top. The walls of the cathode tunnel should consist of a material that is porous enough to permit the slow passage of electrolyte through it, and I refer to it herein as a material that is semi-permeable to the electrolyte. It should be a poor conductor of electricity, but easily permeable to the electric current when saturated with electrolyte. One substance that fulfills these conditions is corborundum comminuted and having the granules bound together by a suitable cement, such as bakelite. In so far as its functional efficiency is concerned, the cathode compartment may be molded in one integral mass, or built up of slabs. For convenience of manufacture I have constructed it of assembled slabs, cemented at the joints. It has already been said that the cathodetunnel conforms approximately in cross section to the cathode ribbon, being but slightly wider than the thickness of said ribbon. Three feet is a suitable length, but this dimension may be varied, like the others, as dictated by the necessities of use.

The anode compartment occupies the space on both sides of the cathode compartment, and the electrolyte, when the apparatus is in operation, stands above the top of the cathode compartment and completely submerges it. The anode material occupies much of the space in the anode compartment on each side of the tunnel-like cathode compartment. In case it is desired to deposit layers of copper, the anode may be of coper shot, or small balls 29, resting between P and-against the walls of the cathode compartment 27 and copper plates 30, to which the positive lead from any suitable source of current electricity may be connected. To keep the electrolyte from teeming over the sides of the cell, drain pipes 31 are provided. These maintain the electrolyte during operation at a constant level which is above the top of the cathode chamber, and drain the overflow into the catch tank 11.

From compartment 31 in the elevated reservoir 12, electrolyte 25 sinks through the standpipe 16, gathering .speed as it passes through the restriction 32 into the branches 33. Each branch 33 delivers to one of the nozzles 34, each of which is designed to have Venturi characteristics or such characteristics as to deliver the electrolyte entering it through the-narrow entrance orifice 35 into the [slot 23 and thence into the cathode tunnel at extremely high speed. As illustrated in Fig. 5, one nozzle 34 delivers into the slotat one side of the cathode ribbon 24, while the other nozzle delivers into the slot on the other side of said ribbon. The nozzles 34 are separated from each other by a narrow passage 36 of dimensions adapted to allow the cathode ribbon to move between them. F ig. 5 shows the nozzles view from above, the top plate having been partly broken away. They may be made of glass, vulcanite, acid-proof metal, glazed porcelain or other suitable material, and may be made integral or'of parts'cemented or fused together, according to convenience of manufacture. The communication between the high speed nozzle or nozzles and the cathode chamber is a closed one in order that the high pressure requisite to the required high speed of the electrolyte may be attained.

The electrolyte, delivered into the narrow cathode tunnel at exceedingly high speed on each side of the cathode ribbon, aids in keeping the flexible ribbon hentered in the tunnel, because the pressure is equal onboth sides and quite adequate to straighten any slight bulges or bends in the metalribbon.

It travels at high speed and pressure. With said compartment at high speed, emerging from the slot 23 in the rear end wall 21 of the cell. A minor portion of the electrolyte passes through the porous wall of the oath ode compartment and enters the anode compartment, flowing through it much more.

slowly as a separate stream, said anode 'compartment in the illustrated embodiment being open to the atmosphere. The quantity of the electrolyte flowing through the anode compartment shouldbe about ten per cent of that flowing in the cathode tunneh and this percentage may be quite accurately attained by using a proper size of granules and suitable binder in the composition of the tunnel walls. None of the electrolyte in the anode compartment can rejoin the stream in j the cathode compartment because ofthe high pressure existing in the latter.

As the pressure of the electrolyte drops only slightly in passing through the cath compartment, once the full "speed of the stream has been attained, it spurts from the slot 23 in the rear end'wall 21 of the cell with great velocity. In order to dissipate the kinetic energy in the jetting stream of electrolyte, a baffling compartment 37 is provided' at the rear end of cell 10. The rear wall 39 of this bafiling compartment has a slot 38 which is in aliner'nent substantialy with the slots 23 in the end walls of the cell,

through which the cathode strip travels. A removable plate 40 covers the upper side of compartment 37, and the rear wall 39 is cut away as at 41 so as to form an outlet its or weir for the electrolyte that does not escape through the slot 38 around the cath ode, but wells upward in the chamber. 1 Another battling compartment 42 having an opening at 43 in its bottom and-having a rear wall 44, provided with a slot 45 for the passage of the now compound strip 24*,

prevents the spattering about of the electrolyte issuing from the slot 38, which encounters the mass falling over the'upp'e'r edge of wall 39 at the cut away 'part 41 and thereafter the rear wall 44015 the rear most bafiling chamber. The electrolyte issuing from the cathode compartment now drops through the lower opening 43 into the catch tankll, to join with that flowing from the anode'compartment through the over- 'fiow pipes 31.

Catch tank 11 preferably has a floor 46 that inclines downward toward a sump 45 at the forward end, whence the electrolyte is removed through the intake pipe 14 of the acid-proof pump 13, which forces it through the pipe 15 into the elevated reservoir 12.

The elevated reservoir 12 is shown as divided by a partition 47, which does not reach to the top of the reservoir, into compartments 48 and 31. Below the upper edge of partition 47 there is shown a filter plate or layer 49, which may be composed of silica sand, granular carborundum or other suitable material. The electrolyte filters through said filter late into the compartment 31, whence it alls by gravity into the standpipe 16. Thus the electrolyte may be purified of sediment b settling in the compartment 48 and by ltration in compartment 31.

The cathode 24, as before stated, may be of indefinite length. Commercial rolled strips of co per suitable for this use, five one-thousan ths of an inch in thickness, are obtainable as long as 400 feet. Such a strip in coil form may be mounted on spool 17 which may rotate with any desired frictional resistance'on its stand 50. One endof said cathode strip may bethreaded through the cell and attached to the reel 18. The reel 18, v to secure best. results, should be evenly rotated at a speed predetermined according to the thickness of deposit re u-imd and the current density utilized. 1* have shown, somewhat" conventionally, a power drive comprising a motor 51, the speed of which may be accurately controlled driving, through a reducing gear if desired, a worm 52 in mesh with a worm wheel 53 on vertical shaft 54 with which the reel 18 rotates. The cathode strip may be coated with any of the coatin s usually applied to cathode surfaces. Sodium sulphide has been found satisfactory for the purpose.

After the entire. length of cathode ribbon flows through the cell in two streams of differential pressure, the high pressure stream flowing in contact with the cathode and the low pressure stream flowing in contact with the anode or anode material; that the cathode is inclosed and completely separated from the anode material by a partition freely permeable to the electric current but more difiicultly permeable to the electrolyte; that almost any pressure desired, subject to Thus extremely high density currents, far i above 300 amperes er 8%11818 foot, can be utilized for the rapid pro notion of electrolytic deposits.

A system composed of ,a plurality or battery of units of the kindv described eifects great economies in electro-deposition of metals as compared with the usual practlce using relatively low current densities. Very much less space is required for the same output, less electrolyte-need be used, a much smaller reserve supply of anode metal need be kept on hand, and less labor is required. Each cell is only a small fraction of the size of that which would have to be employed where the usual low current densitles are utilized. The amount of electrolyte in use can be reduced. In proportion as the current density is increased. The amount of "dead metal in the form of anode material necessary to be kept in reserve can be very much reduced. The amount of labor and supervision necessary for a given output per day is less. The great expense of maintaining highly cathodes, of great size usual in the production of long strips electrolytically) is entirely eliminated, since in this process a standard rolling mill product may be used, which, if it becomes damaged, can be worked up into standard manufactured products.

Although for purposes of exemplification olished cylindrical I have illustrated and described a specific I What I claim and desire to secure by Letters Patent of the United States is:

1. The process of de ositing metal electrolytically upon a cat ode surface, using extremely high cathode current densities, which consists in completely separating the anode and cathode in the cell by a; semipermeable, no'n-conducting partition of low electrical resistance when saturated with electrolyte, thereby forming two compartments affording no passage for electrolyte from one to the other except through said partition, and forcing electrolyte through the cell in two streams under differential pressures, the higher pressure being in the cathode compartment.

2. A process of depositing metal electrolytically upon a cathode surface, using ex tremely high cathode current densities, which consists in completing separating the anode and cathode in the cell by inclosing the cathode in a tunnel-like compartment having a wall of porous, non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, thereby forming two compartments affordingl no. passage for electrolyte from one to t e other except through said wall and circulating the electrolyte continuously through the cell" in two streams under diflzerential pressures, the'higher pressure being in the cathode compartment.

The process of depositing metal electrolytically upon a cathode surface, using extremely high cathode current densities, which consists'in completely separating the anode and cathode in the cell by porous, non-conducting partition, semi-permeable to the electrolyte and of low electrical resistance vwhen saturated with electrolyte, thereby forming twocompartments, affording nopassage. for electrolyte from one to the other except through said partition, forcing the electrolyte through the cell in two distinctstreams, the major portion being forced at high pressure and high speed through the cathode compartment, which is closed except where the electrolyte enters and leaves it, and the lesser portion being forced through the partition and through the anode'compart'ment, which is open and at atmospheric pressure.

4. The process of depositing metal electrolyticallyupon a cathode surface, using extremely high cathode current densities, which consists in enclosing the cathode in a tunnel-like compartment, thereb completely separating the cathode from t e anode in the cell, said compartment having a wall of porous, non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with the electrolyte thereby forming two compartments affording no passage for electrolyte from one to the other except through said wall, and forcing the electrolyte through the cell in two distinct streams, the major portion be: ing forced at high pressure and high speed through the cathode-enclosing compartment, and the lesser portion being forced through the wall of said cathode compartment, and through the anode compartment, which is under lower pressure than the cathode compartment.

,5. The process of depositing metal electrolytically upon a cathode surface, using extremely high cathode current densities, which consists in completely separating the anode and cathode in the cell by a porous, non-conducting partition, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, forcing the electrolyte through the cell in two distinct streams, the major portion being'forced at high pressure and at a speed of not less than ten feet per second through the cathode compartment, which is closed except where the electrolyte enters and leaves it, and the lesser portion being forced through the anode compartment, which is under lower pressure than the cathode compartment.

6. The process of depositing metal electrolytically upon a cathode surface, which consists in using cathode current densities in excess of 300 amperes per square foot, completely separating the anode and cathode in the cell by a porous, non-conducting partition, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, forcing the electrolyte through the cell in two distinct streams, the major portion being forced at high ressure and high speed through the cathode compartment, which is closed except where the electrolyte enters and leaves it, and the lesser portion being forced through the anode com- 1 extremely high cathode current densities which consists in completely separating the anode and cathode in a cell by enclosing an elongated cathode of ribbon form in a .tunnel-like compartment, having a porous, nonconducting wall, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said tunnel conforming in cross section to the form of the cathode and being but slightly larger than said cathode, and forcing the major portion of the electrolyte at high pressure and high speed into the said tunnel on both sides of the ribbon cathode, in order to center the same within the tunnel.

8. The process of depositing metal electrolytically upon a cathode surface, using extremely high cathode current densities, which consists in completely separating the anode and cathode in the cell by enclosing an elongated, flexible cathode of ribbon form in a tunnel-like compartment of porous, nonconducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said tunnellike compartment conforming in cross section to the form of the cathode and being slightly larger in cross section than the oathode, and forcing the electrolyte through the cell in two distinct streams, the major portion being forced at high pressure and high speed through the cathode compartment on both sides of the cathode, thereby centering 9. The process of depositing metal electrolytically upon a cathode surface, which consists in completely separating the cathode froman anode by a semi-permeable nonconducting partition of lowelectrical resistance when saturated with electrolyte thereby forming two compartments aiiording no passage for the electrolyte from one to the other except through said partition and applying electrolyte moving at. high speed to the cathode surface while maintaining a pressure on the cathode side of the partition higher than that on the anode side.

10. In an electrolytic apparatus, a cell comprising an anode and acathode compartment completely separated by a porous par-- tition of non-conducting material semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, means for maintaining a difference of pressure between said anode and cathode compartment consisting of a: tunnel passing through said anode compartment from end to end, said cathode compartment having a porous wall of non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, and a cathode within said compartment, said compartment being of a cross section corresponding to the cross section of the cathode, and but slightly larger.

' 13. In an electrolytic apparatus, a cell, comprising an anode compartment and a cathode compartment consisting of a tunnel passing completely through said anode compartment and open at each end at the exte rior of the cell, said cathode compartment having a porous wall of non-conducting ma terial, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, the passage through said tunnel being of an oblong form in cross section, and a ribbon form cathode inclosed within said tunnel and nearly filling it, there being spaced wear-resisting guides, of material inert to the electrolyte, for guiding and centering the ribbon cathode.

14. In an electrolytic apparatus, a cell, comprising an anode compartment and a cathode compartment, completely separated from each other by a porous wall of nonconducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said cathode compartment being completely closed except that'it. is provided with an inlet andioutlet for admitting and discharging electrolyte, and means comprising a nozzle in closed communication with the cathode compartment for forcing electrolyte under pressure into the inlet opening and through said cathode compartment.

15. In an electrolytic apparatus, a cell, comprising an anode compartment and a cathode compartment consisting of a tunnel passing completely through said anode compartment and open at each end at the exterior ofthe cell, said cathode compartment having. a porous wa'll'of non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte-, the passage through said tunnel being. of an oblong form in cross section, and a ribbon form cathode inclosed within said tunnel and early filling it, a pair of nozzles, one on each side of the ribbon cathode, and means for forcing the electrolyte through said nozzles, under pressure, into said tunnel.

16. In an electrolytic apparatus, a cell, comprising an anode and a cathode compartment, completely separated from each other by a porous Wall of non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said cathode compartment being completely closed except that it is provided with an inlet and outlet for admitting and discharging electrolyte, and a slotted bafiling chamber in communication with the outlet, adapted to dissipate the kinetic energy of the outflowing electrolyte and prevent spalshing.

17. In an electrolytic apparatus, a cell, comprising an anode and a cathode compartment, completely separated from each other by a porous wall of non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said cathode compartment being completely closed except that it is provided with an inlet and outlet for admitting and discharging the electrolyte, and a. slotted bafliing chamber in communication with the outlet, adapted to dissipate the kinetic energy of the outflowing electrolyte and prevent splashing, said chamber having aweir-like orifice at its upper portion for permitting outflow of the electrolyte.

18. In an electrolytic apparatus, a cell, comprising an anode and a cathode compartment, completely separated from each other by a porous wall of non-conducting comprising an anode and a cathode compartment, completely separated from each other by a porous wall of non-conducting material, semi-permeable to the electrolyte and of low electrical resistance when saturated with electrolyte, said cathode compartment being completely closed except that it is provided with an inlet and outlet for admitting and discharging the electrolyte, a catch-pan underneath the cell adapted to receive electrolyte discharged therefrom, a tank ele-'- vated above the cell, a pump for delivering elcctrol te from the pan to the tank, and an outlet rom the tank in closed communication with the inlet of the cathode chamber.

In testimony whereof, I hereto afiix my signature.

HERBERT G. HARRISON.

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