US2395437A - Apparatus for the electrolytic treatment of moving strips of metal - Google Patents

Description

Feb. 26, 1946. w. M. VENABLE APPARATUS FOR THE ELECTROLYTIC TREATMENT OF MOVING STRIPS OF METAL Filed Feb. 1, 1940 2 Sheets-Sheet 1 Feb. 26, 1946. w. M. VENABLE 2,395,437

APPARATUS FOR THE ELECTROLYTIC TREATMENT OF MOVING STRIPS OF METAL Filed Fe. 1940 2 Sheets-Sheet 2 21 22a x l 1 0 Eli-1 1 f: EEEf-f F 24a 25a 26a I Z Y INVENTOR Patented Feb. 26, 1946 APPARATUS FOR THE ELECTROLYTIC TREATMENT OF MOVING STRIPS OF METAL/J" William Mayo Venable, Pittsburgh, Pa., assignor to Blaw -Knox Company,

poration of New Jersey Application February 1, 1940, Serial No. 316,817

3 Claims.

This invention pertains to the treating of continuous metal material such as strips and sheets or wire.

This invention is especially adaptable for treating metal strip when the velocity of strip movement is so high that submergence of a moving strip in a pool of liquid gives rise to serious difliculties on account of the carrying forward of large quantities of liquid by the moving strip.

In a more specific aspect, my invention deals with procedure and apparatus for cleaning metal strip to remove grease and other impurities prior to further treatment, such as coating it with metals or with lacquer, enamels, etc., and also to pickle metal strip before galvanizing. In general, it applies to the cleaning of metal to remove undesirable deposits thereon whether in the nature of grease or scale or some other substance.

The present practice in the art of cleaning metal strip is to pass it downwardly into a pool of treating solution to submerge it within a definite liquid level while it undergoes treatment. The present invention avoids the need of this by applying the treating liquid to upper and lower surfaces of the strip while it is in motion. The means for applying the treating liquid without deflecting the strip from a horizontal path are important features of the present invention.

It is also usual in the art to facilitate the action of a chemical bath upon impurities on the strip by passing current through the bath to and from the strip. The present invention provides means of accomplishing such a result without submerging current supply means such as electrodes in the bath by applying cleaning liquid or fluid between the electrodes and the strip on one side only of each electrode.

Another object of my invention is to provide procedure for cleaning metal strip whereby the strip may, in effect, be guided by the cleaning fluid.

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

In the drawings:

Figure l is a top plan view showing an arrangement employing my invention;

Figure 2 is a longitudinal side sectional view in vertical elevation taken along line 11-11 of Figure 1;

Figure 3 is a cross-section view in elevation taken along the line III-III of Figure 1;

, the strip and thereabove.

Pittsburgh, Fa, a cor- Figure 4 is a perspective view illustrating a suitable adjustable mounting arrangement for element parts of spray units, such as shown in Figures 1-3;

Figure 5 is a longitudinal side sectional view in vertical elevation, similar to Figure 2, but showing another or modified embodiment of my invention.

Figure 6 is a perspective detail showing a unit of Figure-5.

Referring particularly to Figures 1-4, inclusive, the metal piece, that for purpose of convenience has been designated strip, and that represents any suitable metal form or shape such as sheet, wire, etc., is preferably fed continuously; the direction is indicated by arrows; any suitable means such as a roll pair H may be employed. The strip I ll moves progressively past pairs of cleaning units l5. The number of such units can be varied, as desired, although for the purposes of illustration I have shown a repre-' sentative number of four. One or more collecting tanks l6, see Figure 3, are positioned beneath the treating units l5 to collect the fluid and to again return it through a pump l7 and a heat exchanger mm a header l9 that supplies the units l5. It is usual to heat an alkali cleaningfiuid to increase its efiectiveness; this is the purpose of the heat exchanger I 8, which is supplied with heat from any convenient source, not shown. The pump I! may be employed to provide a suitable pressure to circulate the fluid and to apply it to the strip Ill;

The representative units l5 (A, B, C, and D) comprise substantially similar upper and lower halves, see Figures 2 and 3. The upper half or casing, indicated in general by 20, extends across The space between the strip l0 and the part 20 is supplied with cleaning liquid or fluid through an inlet connection 2|. In Figure2', the part 20 is shown with a depression, groove or channel 26 in its underside for providing a. ready distribution of the liquid over the surface of the strip. The strip Ill moves to the right as shown in Figure 2 in such a manner that the liquid or fluid contacting the strip is advanced between the strip and the electrode 24. A further restriction of the space allowed for the passage of the strip B, C, and D. The apparatus may be so constructed and proportioned that a proper distribution of flow is secured through the parts. Otherwise, regulating valves 23 and 23amay be introduced into the various branch lines leading to the several inlets 2| and 2Ia. Between the header [9 and the several inlets 2| and 2m, I introduce tubing of non-conducting material 22 and 22a to prevent passage of current through the tubing, itself. The upper and lower parts of the units A, B, C, and D are of similar construction and the same numerals have been used throughout, although a suflixes have been employed to distinguish the lower parts; further description thereof is therefore unnecessary.

As shown particularly in Figure 4, the posi-- tion of the electrodes 24 and 24a or their distance from the sheet II] can be adjusted by loosening nut and bolt means 28 that secures the electrodes to slotted mount brackets 21. In like manner, the position of the orifice restricting member or element 25 can be adjusted by loosening mounting bolts 28.

There are electrodes on each of the units A, B, C, and D. Some of these are connected to a positive terminal of a suitable electrical source such as a generator (not shown) and others to the negative terminal. The connections to the current supply are so made that opposite sides of the strip are equally treated. Preferably the j number of electrodes above th strip is equal to the number below, and half of the electrodes on each side are positive and half negative. Preferably, but not necessarily, the electrodes are placed in pairs, the members of a pair being opposite. This arrangement is shown in both Figures 3 and 5. In Figure 5 opposite electrodes .in any one pair are shown as of the same polarity, adjacent pairs being of opposite polarity. With this arrangement the current flows from both electrodes in unit A through the solution to'the strip, thence through the strip to unit B, where it passes again through the solution to the electrodes in B. If desired the parts and the current used may be so proportioned that the current supplies all the heat to maintain the desired temperature, rendering the use of the heat exchanger l8 unnecessary. Ordinarily, however, it is cheaper to supply heat from some other source, and that supplied by the current is merely incidental.

Polarity of the. electrodes is not indicated in Figure 2. It may be the same as in Figure 5. On the other hand, by making the parts '25 and 25a in Figure 2 of relatively non-conducting material, short-circuiting' of current by contact of the moving strip with both upper and lower electrodes at the same time is prevented, and opposite electrodes may be made of opposite polarity. Thus the upper electrode in A may be positive and the lower negative, while the upper electrode in B is negative and the lower positive. With this arrangement the current passes directly through the strip, in one direction at one pair of electrodes and in the opposite direction at the next succeeding pair, the amount of current passing lengthwise the strip being negligible.

As previously pointed out, the pipe connections 22 are preferably of'non-conductor material. In like manner, the housings 20 and 20a may be but are not necessarily of non-conductor material. The orifice restricting members 25 however, are preferably of non-conductor material and, of course, the electrodes 24 are of conducting material. The nor-conductor material may beof any suitable type such as wood, rubber. fabric, or plastic. I

In the operation of the arrangement shown in Figure 2, the strip I0 is moved continuously, as indicated by the arrows, and liquid is applied adjacent the point of entrance of the strip to each of the units 15 (A, B, C, and D). The movement of the strip carries the liquid along'with it in the direction of the electrodes 24 and, 24a. In this manner, the upper and lower portions of the strip are covered with fluid and subjected to a cleaning action. The spaces between the strip and the housings 20 and 20a are thus substantially filled with liquid, which is carried toward 25 and 25a by frictional surface contact with the strip, and thus acquires velocity which will be greatest in that portion of the liquid in immediate contact with the strip. The arrest of this velocity in portions of the liquid by 25 and 25a produces pressure between the housings and the strip. Some of the liquid will be carried with the strip between it and 25 and 25a. The rest of the liquid supplied at 26 and 26a will be ejected laterally at the open side edges of the housings. It is obvious when 25 and 25a are adjusted to a suitable distance apartthat if the strip approaches closer to one than to the other, the liquid pressure on the side of closest approach willbe greater than that on the opposite side, thus tending to restore the strip to its normal or medial position. The greatest activation of the liquid will, .of course, be adjacent the electrodes and a lesser action will be effected along other length portions of the strip. Although during its movement, the strip will not normally touch either of the guide members 25, these members serve to prevent a mechanical contact between the electrodes and the strip and to prevent undue deflection of the strip during starting and stopping or maladjustment of the strip propelling mechanism.

In the arrangement of Figure 5, I have shown units IS (A', B, C, and D'.) having all-metal upper and lower housings 30 and 30a; a corrosion-resisting metal or alloy is preferably employed. These housings carry liquid supply inlet headers 3| which are connected to the pipe connections 22 in the same manner as the arrangement of Figure 2. In this embodiment, I prefer to connect the upper and lower opposite parts 30 and 30a at connections 33 to the same terminal of the current source in order to avoid any direct short-circuiting of current through the narrow or converging portions 34 and 340.. With this arrangement, the alternate units A, B, C, and D will be of different polarity and, as explained before, the current will pass through the strip from one unit to the other. In the units of Figure 5, inlet headers 3l-are open to supply liquid to the strip as freely as in Figure 2, and as the entire casing 30 is of conducting material. it is apparent that the flow of current to the strip will vary in density or intensity in accordance with the electrical resistance, and thus, generally. in inverse proportion to the distance between a particular portion thereof andthe strip. The shell or housing is shaped to provide restricted outlets 34 and 34a.

The contro1 valves 23 and 23a for controlling the quantity of liquid may be employed as described in connection with Figure 2. It will be readily observed that with the arrangement shown in Figure 2 as well as in Figure 5, the' liquid thereof.

The arrangement of Figure is particularly adapted to take advantage of what may be termed such self-centering action of the cleaning liquid. As long as the strip continues to move, it will thus be practically prevented from making contact with adjacent portions such as 34 and 34a of the cleaning units. However, should contact be made with this arrangement, it would not be of serious import or long duration.

It is obvious that if liquid is supplied in sufficient quantity to all of the devices A, B, C, and D, it cannot all be carried with the strip. That which cannot pass through the orifices with the strip will flow laterally outwardly from edges of the strip. New and practically clean liquid is supplied at the units, themselves. Most of the impurities and those resulting from chemical action that are notsoluble will be ejected from the strip at the intermediate positions between units resulting in a series of electrochemical treatments of practically equally active solutions in each of the several units.

It will also be obvious that in the case of the embodiment of Figure 2, the part may be made of a suitable non-conducting material or placed at a sufficient distance from themoving strip that the resultant resistance will prevent the passage of much liquid therebetween. The electrodes 24 and 24a are of any suitable desired width and are set as close to the strip as practice will permit. It is obvious that very high current densities can be obtained in this manner and it is a known fact that large currents are beneflcial in making an electro-chemicaltreatment most effective.

In both forms of the invention which are illustrated, the metal strip is maintained under tension; baffle means are provided close to the surface of the strip: and more liquid is supplied to the strip than can be carried with the strip past the baflle means, whereupon pools of turbulent liquid are formed adjacent the baffles, and in this region of turbulence the greatest electrolytic action takes place while excess liquid is forced sidewise ofi the edges of the metal strip.

It will be apparent to those skilled in the art that novel features of my invention are particularly applicable where the strip is moving rapidly.

. It will also be apparent that I have been the first to utilize velocity imparted to the liquid by the movlngt'strlp' to produce pressure against the strip where'the flow of liquid with the strip is partially interrupted. The open side edges of the casings permit liquid in excess of that carried through the. openings to pass laterally across and away from the moving strip.

Although for the purposes of illustration, I have shown representative preferred apparatus arrangements and layouts for effecting the results of my invention, it will be apparent to those skilled in the art that many suitable arrangements, modifications, additions, and subtractions may be made without departing from the spirit and scope of the invention as indicated by the appended claims.

I claim:

1. Apparatus for the electrolytic treatment of a rapidly moving strip of metal comprising means for rapidly moving the strip under tension longitudinally with its transverse axis horizontal, a succession of horizontal baflie means along the path of travel of the strip on each side thereof and spaced close to but out of contact with the strip, said baflie means being of a length at least coextensive with the full width of the strip, a housing surrounding the strip adjacent each baflie means, said housings being spaced apart to provide openings at the lateral side edges of the strip, means in advance of each bafile means for supplying electrolyte to the housings to be carried by the strip toward and beyond the baiile means, said means for supplying electrolyte operating to supply the electrolyte at a rate faster than said electrolyte can be carried under the bafile means whereby a turbulent pool of excess electrolyte is established and maintained in the housings across the leading face of each of the baflie means and excess electrolyte is flowed sideways beyond the edges of the strip, means electrically connecting said bailie means to a source of current whereby electrolytic action is concentrated in the liquid adjacent the baflle means.

2. Apparatus recited in claim 1 wherein said housings have lateral extending and confronting channel portions for facilitating s'idewise distribution of the electrolyte.

3. Apparatus for the electrolytic treatment of a strip of metal comprising means for rapidly moving the strip under tension longitudinally with the transverse axis of the strip horizontal, a plurality of transverse baflle units extending crosswise of the strip and being at least coextensive with the full width of the strip, each of the baflle units comprising a baflleportion which is close to but out of contact with the strip and a housing portion enclosing the surface of the strip adjacent each baiile portion, said housings being spaced apart to provide openings at the lateral side edges of the strip, each baflle unit having an electrically v conductive area across the full width of the strip,

means for supplying electrolyte to the housing portion of each baflle unitto b carried by the strip toward and beyond the baflie portion, said means for supplying electrolyte operating to supply the electrolyte at a rate faster than said electrolyte can be carried between the baflle portion and the strip whereby a turbulent pool of electrolyte'is established and maintained in the housing portion of said units across the leadin face of each of the baffle portions and electrolyte is flowed sideways beyond the edges of the strip, and means for causing a current flow between the conductive areas of different units and the strip whereby electrolytic action is concentrated in the liquid adjacent the baflle means, said units being disposed in pairs, members of apair being on, posite one another on opposite sides of the surface of the strip and being of the same polarity.

WILLIAM MAYO VENABLE.

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