US2446548A

US2446548A - Contact roll construction

Info

Publication number: US2446548A
Application number: US519429A
Authority: US
Inventors: John S Nachtman
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-01-16
Filing date: 1944-01-24
Publication date: 1948-08-10
Anticipated expiration: 1965-08-10

Description

Aug. 10,1948.

J. s. NACHTMAN CONTACT ROLL CONSTRQQTION Original Filed Jan. 16, 1939V r l l y /l'iil'wiwiiii ll 2 Sheets-Shadi l atte/wap Aug. l0, 1948. J. s. NACHTNIAN 2,446,543

CONTACT ROLL` CONSTRUCTION original Filed Jan. 1e, 1939 2 sheets-sheet 2 WQMWM" Patented ug. 10, 1948 unirsi) srArgs PATENT? @mcg Original application January 16, 1939, Serial No.

251,065, now Eatent No. 2,341,157, dated February, 19M. Divided and this application January 24, 194i, Serial No. 519,429

s citiamo. (ol. 2114-211) This invention relates to electro baths, and particularly, to the handling oi strip material while subjecting it to an electro-treating process, such as electroplating. I have particular reference to suitable contact roll apparatus for continuously electroplating or treating metal strip and the like; and this application is a division of my copending application Serial No. 251,065, filed January 16, 1939, now Patent No. 2,341,157, granted February 8, 1944,

I have found that there are many difficulties encountered in providing a suitable arrangement for the purposes enumerated. In electro treatment. the strip will constitute one of the electrodes (in plating, the cathode) and other means will constitute the other electrode (in plating,

the anode).

The contact roll pparatus of the prior art possesses the following serious disadvantages. among others, which have made it impractical to produce a uniformly high grade product by a continuous operation:

(a) In continuous plating operations, high current densities per unit of surface being plated .must be employed to expeditiously deposit'vcoatings of desired thickness; and. great lengths of strip must be subjected to the plating operation for comparatively long periods of time. The length of'strip being subjected to the plating operation at any one instant may in practice, be several hundred feet. In order to plate such a length oi strip while in motion, the stripbeing the cathode. it is necessary to establish electric contact with it at a'number of points spaced along its length. This is usually done by rceving the strip over two sets of rolls, an upper set and a, lower set, contact for the plating current being made through the upper set of rolls, over which the strip passes. With this arrangement it is dif-- iicult toobtain a good electrical connection between contact rolls and the metal strip, especially after the strip has been partially plated. I'lihe strip passes approximately half-way around the contact roll or rolls (upper set), and as it is wet with the electrolyte, the current, in going from. the roll to the strip, must pass through a thin lm of electrolyte. This causes deposition oi metal on the roll instead of the strip, and may even remove plated metal from the strip while passing over the roll. This is undesirable. as it is detrimental to the apparatus and makes it impossible to obtain a high grade product.

(b) Pulling the strip from one end thereof over a number of rolls subjects it to high flexing and tensional stresses. This is true even if the rolls are turned without friction, but as the current is conducted to the rolls through a slip ring or brush system, which increases the resistance to turning of the rolls, the strip tension is of considerable magnitude. If the rolls must be turned by friction with the strip, slip of stripv where it makes contact with the rolls may occur. It the strip surface is soft as for example electroplated with a soft metal such as tin, any such slip may damage the plating, especially in the initial stages, `where the plating is very thin, and may not have completely covered the base stock of the strip.

(c) The contact rolls themselves are particularly weak portions of such an apparatus and are a constant source of trouble because of limitations in material available for their construction.

Those that are made of material that possesses good electrical properties and have suiiicient niechanical strength to withstand the stresses to which they are subjected in carrying the strip, usually are subject to corrosion by the electrolytes; whereas, those that are constructed of good corrosion-resisting materials such as carbon and some cast alloys, are usually not good conductors and do not possess sufiicient mechanical strength to withstand the .stresses in carrying the strip.

(d) Also, serious dimculties are experienced in making electrical contact between rotating contact rolls over which the strip passes, as heretofore constructed, and the stationary current-supplying brushes because the contact surfaces .are exposed to the electroplating solution. This causes a loss in voltage, which results in excessive heating and other contact ills. This condition is further aggravated because many of the most desirable solutions in use today react electrolytically with the brushes.

It is accordingly a general object of my invention to provide a commercially practical solution of the difculties and 4problems presented in prior art contact roll construction.

Another object of the invention is the provision of contact roll apparatus for continuouslyelectroplating strip material that will emciently and uniformly conduct eiectroplating currents thereto at several regions throughout its length as the strip passes through the bath or baths, with a minimum of resistance.

A further important object oi the invention is the provision of an improved contact roll construction for electroplating strip material continuously that employs a, plurality of rolls, driven at a suitable synchronous peripheral speed for gripping the strip at spaced points throughout its length and smoothly propelling the strip through the electroplating steps without subjectlng the strip to tensional or twisting forces.

A further object is to provide a novel contact roll construction for use in electroplating or electrochemical processing apparatus and which embodies a totally enclosed current-conducting mechanism which is not contaminated by the electro-bath solution.

A still further object is to provide a hollow contact roll for use in electroplating apparatus for strip material which embodies internal brushes contacting an inner surface of said roll at a region in proximity to the point of contact of the strip material with the outer surface of the roll, whereby the path oi current through the wall of the roll is of minimum length and the brush pressure counteracts the pressure against the outer surface of the roll.

Moreover, it is an object of the present invention to provide a novel contact roll construction for use in electroplating and electrochemical processing apparatus, which embodies an enclosure for the current conducting brush mechanism through which cooling fluid may be circulated.

These and other objects of my invention will appear to those skilled in the art from the drawings, the description, and the appended claims.

Although for the purpose of illustration I particularly refer to electroplating operations, it should be understood that many of the novel features of this invention are equally applicable to electro-pickling and other types of electro-bath treating operations.

In the drawings,

Figure 1 is a fragmentary vertical sectional view through electroplating apparatus embodying the improved contact roll construction;

Fig. 2 is a fragmentary vertical longitudinal sectional view taken substantially along the line 2`2 of Fig. 1, looking in the direction of the Fig. 3 is a longitudinal sectional view through the contact roll construct-ion employed in the apparatus of Figs. i and 2;

Fig. 4 is a transverse sectional view taken on the line (-4, Fig. 3;

Fig. 5 is a longitudinal sectional view sil'nilar to Fig. 3, but illustrating a modied form of contact roll of the invention; and

Fig. 6 is a transverse sectional view taken on the line 6 6 of Fig. 5, looking in the direction of the arrows.

Similar numerals refer to similar parts throughout the various figures of the drawings.

The apparatus comprises a tank or container T through which the strip material S is fed in a sinuous path. The strip material is reeved over and under respectively, a series of upper rolls 1 and 8 and lower rolls (not shown) submerged in the solution in the tank; the rolls 1 and 8 being above the surface of the solution.

Above the strip where it passes over each roll 8 is a contact roll 1, by means of which electrical contact for the plating current is made with the strip, instead of through roll 8, as is the practice usually followed hitherto. The rolls 1 are preferably driven at the same peripheral speed so as to propel the strip smoothly through the bath. As the strip emerges from the bath for the last time, it passes through a squeegee assembly Q for removing the adhering electrolyte therefrom.

An anode electroplating current is applied to a plurality of anodes A which are suspended in the bath between the vertical reaches of strip S.

the tank adjacent the anodes A and also to flush strip S above the level of the electrolyte for dislodging adhering extraneous matter, both as it is entering and emerging from the electrolyte.

The tank Tis generally rectangular in form and comprises side walls, a bottom wall and end walls. For the purpose of simplifying the illustration of the invention, I have shown the strip as making only two complete passes through the electrolyte, but it is to be understood that in actual practice the tank and other parts will be so designed plurality of pairs of perforated pipes Il.

as to cause the` strip to make any suitable number of passes through the electrolyte; in some instances several hundred feet of strip material may be immersed in the tank at one time.

A circulation pipe communicates with the bottom of the tank through which the electrolyte is fed to an electrolyte reconditioning and heat exchanging apparatus, of any suitable character, for purifying the electrolyte, restoring it to proper strength and bringing it to the requisite electroplating temperature.

The electrolyte is returned to the tank by way of a pair of spray pipes il and a pair of recirculation pipes i0. Spray pipes 9 may extend longitudinally of the apparatus and they are joined by a The pipes of each pair are disposed either side of the path of travel of the strip S and the perforations are directed downwardly at an angle to the horizontal for flushing the strip and cleansing it of any adhering material. Pipes I0 are each joined to a horizontal pipe i2 and, as seen in Fig. 1, each pipe I2 extends longitudinally on either side of the path of travel of strip S. Joined to pipes i2 at spaced intervals are vertical pipes I3, each having perforations i4 therein that are directed toward the middle of the tank. The electrolyte issuing from openings i4 supplies fresh electrolyte adjacent the anodes and also keeps the body of the electrolyte in the tank in a state of constant agitation.

The contact roll assemblies and other parts of the mechanism are carried upon a pair of horlzontally extending angle members i5, which extend longitudinally of the apparatus and rest upon a plurality of vertical supports i6. The mechanism preferably is supported upon the independent framework Just described in order that the -tank may notbe subjected to stresses. The tank may, accordingly, be constructed of wood, concrete, brick, steel, hard rubber, or any other material or combination of materials appropriate for use with the .particular electrolyte employed, without special regard for supporting the assemblies and parts. To this end, the bus bars and anodes are also supported upon an independent structure to be hereinafter described.

The contact roll assemblies shown in Figs. 1 to 4, inclusive, are similar in construction and therefore one of them will be described.

Each assembly comprises a contact roll 1, proper, which is mounted for movement to and from an associated strip carrying roll 8.

Referring'to Figs. 1 and 3, each contact roll l is journaled on a sha il, which is carried at each end thereof in an arm t8, which in turn is pilvoted at i9 upon the support 20,;carried by members I5. Shaft il is insulated from members it by means of insulating bushings 2l, and an electrical conductor 22, preferably of flexible design, isconnected to each end of shaft Il for` applying a cathode current to shaft il and to contact roll l in a manner later to be set forth.

Each strip-carrying roll 8 is preferably made of steel and rubber (resilient) covered in order that it may eiect intimate surface engagement be= tween the strip S and the contact roll l. The provision oi a coating or cover that will yield under pressure is an important feature of the present invention; it is. preferably an insulating material. However, the invention is not limited tothe use of such materials, as the surfacing of the carrying roll may be constructed of any other material found suitable for the purpose such as phenolic condensation product impregnated fiber, asbestos or other materials or combination of materials. Each carrying roll is supported on a shaft 23, which latter is journaled at each end in a bearing carried by the support 2t. A slinger 2d is positioned on shaft 23 adjacent each side end of the carrying roll; it functions to lreep the elec= trolyte (with which the carrying roll is coated in normal operation by reason of the strip carrying it out of the tank) from creeping along the shaft and into the bearings.

Each contact roll l is resiliently urged toward a carrying roll, preferably by means of compression springs 25 that act upon extensions 2S of the arms iii. Each extension 26 is apertured and a stud 2l', secured to the support 2B, extends through the aperture and through spring 25 and Ahas a nut 28 threaded thereon, against which the spring 25 abuis. By adjusting nut A28 of each contact roll assembly, the strip can be gripped be- .f

4tween surface portions of the contact rolll and strip carrying roll B in contact with the strip with various degrees of compression. A second compression spring 29 is shown on each stud 2l between extension 2@ and support 2li for opposingl l parts.

Secured to the shaft l'i by a pair of set screws 3d is a pair of anged collars Si. Journaled on each collar Si by means of a bushing 32 is al driven annular-like support member 33 having a slinger 3d, and a reduced cylindrical portion 35 terminating in a seal 36; the latter cooperates with shaft i'l to prevent electrolyte from finding its way into the interior of the drum. The drum supports 33 are preferably made of an insulating material. Extending transversely between and joining each pair of members 33 is a cylindrical shell or drum 3l; it is secured thereto by a plurality of cap screws 38. Drum 3l is, preferably-a seamless copper tube, but it may be made, if desired, of other suitable materials without den parting from the spirit of the invention. A nickel sleeve surface plate 39 is preferably welded to the periphery of drum 3l and is adapted to directly contact the strip S as it passes between the contact rolls. Fitting tightly over the opposite ends of sleeve 39 and welded thereto is a further pair of slinger rings du for throwing the electrolyte clear of the ends of the rollers.

I vof castconstruction. Each member 62 isA provided with a plurality of brush guide openings 43; the brushes d4 are mounted therein to cooperate in direct frictional engagement or contact with the interior of the inner Wall or circumferential surface of the drum 3l. A exible brush' lead 45 is connected to each brush di and is secured to shaft il by means of a cap screw 436. Each brush de is resiliently urged toward the surface of the drum by means of a leaf spring di; one end of the spring di is coiled within a support d, carried by member t2 and its free end il@ is adapted to be apparent that brushes de apply current to the y interior of the drum di in the same region as that where the strip contacts the outside of the? drum. Therefore, as brushes llt are compara-y tively numerous and are uniformly distributed along the transverse length of the drum, the current path through the drum to the strip is oi large cross section and short length, which makes for minimum resistance and current loss and avoids heating of the parts in service.

Another important feature of the contact roll l construction just described resides in the fact that the load of carrying the strip is totally adsorbedby the carrying roll t 4and no severe stresses are imparted to the contact roll. The pressure exerted upon the vContact rolls l is that set up by springs 25; in this manner an electrical and driving frictional contact is provided between the roll and the strip. The brush pressure on the inside of the roll l tends to counterbalance the strip contact pressure on the outside of such roll.

The contact drum therefore is substantially free from strain under serviceconditions, and this permits the use of even relatively brittle materials, such as cast alloys and carbon, etc., which are highly resistant to corrosion by electroplating solutions.

The contact roll supports 33 are preferably constructed of an insulating material which functions as an insulator to prevent current from passing to the roll by way of the bearings.

In ordinary service, the parts efficiently funetion at sufii-ciently low operating temperatures, but in the event that the solutions to be employed are hot, a cooling medium may fbe circulated through the roll, and in Fig. 3 there is lustrated one mode for effecting such a resulf.V

In Fig. 3 the shaft il is hollow and is provided with a cooling medium inlet at its left hand end. In the interior of the roll l, the shaft -is provided with a plurality of ports 5d, through which the cooling medium is adapted to discharge and circulate amongst the brushes inthe left hand end of the roll. A plug 5i of any suitable material is secured within shaft il, approximately midway of its length, by means of a tapered pin 52, to prevent the cooling medium from flowing freely from one end of the shaft to the other. The cooling medium may be any desired fluid, such as cold, dry, compressed air, and after it has passed through ports 5l! and has abstracted heat fromthe brushes in the left hand end of the roll, it circulates amongst the brushes in the right hand end of the roll and is exhausted through a plurality of exhaust ports into the right hand end of the roll and is freely discharged therefrom or through a manifold assembly (not shown) to an air cooler at the suction side of the compressor used.

When it is desirable to operate the contact roll at an elevated temperature, as is .the case in plating some of the metals (iron. for instance) there is likely to be metallic oxidation formed on the inside of the drum 31, thus causing a high contact resistance between the brushes 44 and the drum 31. I overcome this trouble .by injecting a sumcient quantity of a suitable ol'l to submerge the contact area between the brushes ll and the drum I1. The oil performs two functions. (1) It coats the inside surface of the drum 31,' thus excluding air and preventing oxidation of the inside surface of the drum. (2) It also lubricates the sliding contacts between brushes Il and drum I1 without materially affecting the contact resistance between the brushes and the drum.

'The gripping or clamping pressure exerted by springs 25 of the various contact rolls upon the strip may be equal or unequal as desired, depending upon the current to be conducted to the strip and other factors involved. The strip material is looped :beneath the submerged rolls in the electrolyte.

The various contact rolls, whether they are of equal or unequal diameter, are driven at a synchronous peripheral speed by any suitable means, in order that all parts of the strip material will be smoothly propelled through the bath. If driving of the contact roll by contact with the moving strip causes undesirable strip tension. a drive sprocket 54 may be secured by means of a key 55 and s et screw 56 to the reduced end of one of the drum support members .33. as shown in Fig. 3; and the drive sprocket 54 may be driven by means of a sprocket chain from a drive mo-v tor for each conta-ct roll, the motors being synchronized to insure smooth propulsion of the strip through the bath.

Referring to Figs. 1 and 2, a' secondary framework having uprights 51 and horizontally disposed angle members 58 is employed to support the bus bar and anode assembly as follows:

Supported on an insulator assembly 59 and carried by members 58 at each side of the tankV area plurality of transversely extending anode supports 6U that extend across the tank as shown in Fig` 1. A plurality of anode bars A are secured to supports 60 and are submerged in the electrolyte. As seen in Fig. 2, some of the anodes A are located adjacent the downwardly (outer) facing portions of the loops formed by the strip material in the electrolyte and they therefore operate to effect electroplating of the underside of the strip material. Other anodes A are disposed within the upwardly (inner) facing loops of the strip material and electroplate .the upper surface of the Lstrip material. The two groups of anodes preferably are electrically segregated in order that a different plating current can lie/applied to one group or the other to eiect a different electroplate on one surface of the strip.

Supports 60 for some of the anode-s A accordingly are connected at each side of the tank to a bus bar 6i carried in a plurality of insulators 52, which in turn are carried by a plurality of brackets 63 secured to supports 51. Supports 60 for other anodes A extend outwardly beyond bus y bars 5i and are connected to bus bars 54, which also are carried by insulators 52.

In Fig. 5 a modified form of contact roll is shown. the major diiierences between it and the contact roll shown in Figs. 3 and 4 residing in the fact that the brushes are pivoted rather than slldablc in their holders, that a modified cooling arrangement is used, and that anti-friction bear- `ings are used.

A pair of annular-like spaced-apart drum supports ST5 4are journaled on bearings 55 and l1 on shaft Ila; and a cylindrical drum shell 5l having integral slingers 591s secured to the drum supports by a plurality of cap screws 10. A pair of sealing assemblies 1I are associated with drum supports 65 and cooperate with shaft 11a to prevent lubricant from leaking from the bearings into the brushes. A drive sprocket 12 is mounted on one of the drum supports for imparting rotation thereto.

Shaft Ila is provided with a dat-sided lower surface 1'3 (see Fig. 6) that extends as shown in Flg. 5.. -Firmly clamped .to shaft 11a by means` y toward the drum by torsion spring 19. The brush supports also embody notched sectors so that the brush pressure may be adjusted by placing the free ends of the springs in the appropriate notches to give the requisite pressures. In order to prevent pivots 18 from carrying current, a ilexibleshunt cable 8l is connected directly to each brush through the brush support.

The current is supplied to shaft 11a by a flexible-conductor in a manner similar to that shown and explained in the embodiment of my invention disclosed in Figs. 3 and 4. The contact roll is also preferably cooled by a fluid medium which enters a conduit 82 at one end of shaft I1a, passes through a longitudinally extending bore 83, andis exhausted through a plurality of ports B4 provided in shaft lla. The cooling medium may be dry, cold, compressed air; it passes downwardly in the roll along both sides of the shaft i1a and abstracts heat from the brushes and their associated parts. The heated air is exhausted from the roll by way of a plurality of exhaust ports 85, which communicate with a longitudinal passage 85 provided in the shaft: passage 86 communicates with a discharge conduit 81. Y

In this form of the invention, the brushes are completely enclosed and protected against the action of the electrolyte, they are arranged substantially uniformly along the axis of the roll,

and they are urge-d outwardly against the inner surface of the roll in the region where the outer surface thereof contacts the strip under a. pressure that is substantially equal to the contact pressure of the roll with the strip. Therefore. all of the advantages of the previously described form of contact roll are achieved.

It will be apparent to those skilled in the art that the contact rolls of my invention can be employed with advantage in place of contact rolls heretofore used in the art, but that I prefer a roll pair combination such as 1 and 5, in order to incorporate desirable features lof such a roll pair. However, if a contact roll is employed without a strip-carrying roll, I prefer to keep the diameter of the contact roll as small as possible;

e. g., a single roll may be used in electro cleani118.

Although I have illustrated the invention in connection with the electroplating of strip material inthe form of steel or other metallic sheets,

it is to be understood that the novel features thereof are applicable to the electroplating of wire, cable, sheet'and elongated shapes and/or articles. The appended claims therefore embrace my invention as applied to any suitable form of material, designated, generally as strip Also, the contact roll assembly of the invention may be embodied in equivalent forms without departing from the spirit of the invention. For instance, the 'brushes may be secured to the inner surface of the drum and may cooperate frictionally with the stationary shaft. Also, I have illustrated the cathode' current-carrying roll as constituting the roll that is movable toward and away from the carrying roll under the iniluence of spring pressure, but it is to -be understood that the relationship may be reversed and the carrying roll be movably mounted and resiliently urged upwardly toward the novel cur- `rentcarrying roll constructions of the invention.

Also, the roll that has been referred to as the carrying roll may embody the novel enclosed V brush combination of my invention.

The cooling apparatus is especially advantageous where excessive heat is encountered. The use of the cooling system is also advantageous, because by suitably regulating the input and output pressure of the cooling medium, a positive pressure may be maintained in the contact roll during operation such that corrosive fumes and gases evolved from the electrolyte Will be prevented from creeping along the shaft and attacking the bearings.

The novel contact roll assembly of the invention effects an improved method of applying the cathode current to the moving strip, because the thin and highly conductive shell constituting the drum makes a line cont-act with the strip to be plated, and because the brushes bearing against the inrior of the shell along a line in approximate super-position with the line of contact of the shell with the strip, insures a uniiormly distributed current throughout the length of the roll, with a resistance path of minimum length and with the total brush pressure substantially equal to the total pressure of the roll upon the strip. As a result, the shell is subjected to a minimum of distorting stress throughout the operation.

Thus, important features of the present invention in the improved contact roll construction are the enclosing of the brushes to protect them from contact with either the plating solution or vapors, the circulation of a cooling iluid through the contact rolls, and the brush contact aligned with the contact of the roll with the strip.

' An ideal contact roll would be one which would not become heated by the current it conducts. It is of course impossible to make usch an ideal contact roll, but the design of improved con- Y 10 n and with solution, and. therefore, the heat which is generated is taken away rapidly.

Entirely diierent conditions occur when the roll body is extended and the brushes contact the extended end of the roll. In such a construction, the length of the path of current is increased many times, the cross section is diminished and the Lportion of the roll where the most heat is generated never comes in contact with either the strip or the plating solution, and consequently a. considerable temperature rise is experienced. n

By actual calculation it canbe shown that the heating effect in the roll body may be of the order of many times greater in a roll with brushes outside of the roll body as compared with a roll with brushes located inside the roll body directly opposite the line of contact between the moving strip and the roll.

The term electrochemical processing" as used herein and in the claims, includes any electrochemical treatment of a moving metallic strip wherein the strip is connected to -an electric po- Ktential which causes'the electrochemical action tact roll disclosed herein, with the brushes in a n -ed by current is in direct contact with the strip on the strip.

I claim:

1. In electroplating apparatus for continuous strip, including a guide roll for the strip adapted to receive the strip against the surface thereof and to supply electric current thereto, said roll comprising a rotatable cylindrical metallic shell, a stationary electrically conducting shaft extending axially through the shell, means closing opposite ends of the shell around the shaft and including bearing means journaling the shell on the shaft, andbrushes xed to the shaft in electrical contact therewith and in outwardly bearing contact with the-inner surface of the shell along a line adjacent the line of contact between the shell and the strip for supplying current thereto.

2. In electroplating' apparatus for continuous strip, including a pair of opposed coacting rolls adapted to receive the continuously moving strip therebetween, one of said rolls comprising a rotatable cylindrical metallic shell, a stationary electrically conducting shaft extending axially through the shell, means closing opposite ends of the shell around the shaft and including bearing meansv journaling .the shell on the shaft, and

' brushes fixed to the shaft in electrical contact therewith and in outwardly bearing contact with the inner surface of the shell along a line adjacent the line of contact between said rolls for through the shell, means closing opposite ends of l the shell around the shaft and including bearing means journaling the shell on the shaft, brushes xed to the shaft in electrical contact therewith and in outwardly bearing contact with the inner surface of the shell along a line adjacent the line of contact between said rolls for supplying electric current thereto, and means for circulating a cooling medium into the shell in cooling relation to the brushes and for discharging said medium therefrom through the shaft.

4. In electroplating apparatus for continuous strip, including a pair of opposed coacting rolls adapted to receive the continuously moving strip therebetween, one of said rolls comprising a ro- 11 tatable cylindrical metallic shell, a stationary electrically conducting shaftr extending axially through the shell. means closing opposite ends of the shell around the shaft and including bearing means Journaling the shell on the shaft, brushes xed to the shaft in electrical contact therewith and in outwardly bearing contact with the inner surface of the shell along a line adjacent the line of contact between said rolls for supplying electric current thereto, said shaft having spaced longitudinally extending passageways therein in open communication with the interior of the shell about the brushes, and means for circulating a, cooling medium through one of said passageways into the shell and for discharging 1| 1,243,325

said cooling medium through the other of said passageways therefrom.

5. In electroplating apparatus for continuous strip, including a pair of opposed coacting rolls shaft in electrical contact therewith and in outwardly bearing contact with the inner surface oi' the shell along a line adjacent the line of contact between said rolls for supplying electric current thereto.

JOHN S. NACHTMAN.

REFERENCES CITED The following references are of record in the 1 ille of this patent:

adapted to receive the continuously moving strip 20 therebetween, one of said rolls comprising a rotatable cylindrical metallic'shell, a stationary electrically conducting shaft extending axially through the shell, means closing opposite ends of the shell around the shaft and including bearings Journaling the shell on the shaft for turning movement relative thereto, said bearings being conlfined within the closing means for retaining lubricant therearound, and brushes xed to the UNITED STATES PATENTS