US2155392A - Method of forming printing cylinders - Google Patents

Description

April 25, 1939. BALLARD 2,155,392

METHOD OF FORMING PRINTING CYLINDERS Original Filed April 16, 1928 MMW Patented Apr. 25, 1939 l UNITED STATES PATENT OFFICE 2,155,392 7 mz'rnon or FORMING rnm'rmc crmmmas Ernest S. Ballard, Berkeley, alif., assignor to Standard Process Corporation, Chicago, 11]., a corporation of Delaware Original application April 16, 1928, Serial No.

Divided and this application November 30, 1932, Serial No. 645,077

4 Claims. (Cl. 204-6) In the manufacture of such forms, prior to the introduction of the invention of my Reissue Patent No. 17,179, it was customary to provide a base structure, usually in the form of a cylinder, and to provide a thick coating or layer of copper 10 thereon, such layer being applied to the cylinder by electro-deposition. The etched printing surface was formed in this copper coating or layer surrounding the cylindrical base. After the printing form had been used it was the practice to remove so much of the layer of copper as had been affected. by the etching, as by grinding or by the use of acid. In my patent above referred to, there is disclosed a printing form in which the printing surface is formed in a very thin shell that can be readily removed by stripping the I shell from the base there shown. The method disclosed in this patent provides an extremely simple and practicable method of forming printing surfaces and of removing 'or renewing such 5 surfaces, the diameter of the cylinder being maintained constant at all times.

The thin shell of said patent must, in actual practice, be entirely free of imperfections. That is, the electrolytically deposited coating'of metal must be of exactly the same dense and uniform structure and must be absolutely the same thickness at every'point, if grinding and excessive polishing of the cylinder is to be avoided prior to the etching thereof. It has been found thatv the formation of a shell, upon the cylindrical base by electrolytiTacticn, that is free of imperfections and variations in the thickness of the deposit, necessitates special care in the mode of application of the coating, and if the uniform' 40 dense character ofthe coating at every point is to be assured, that the electrolytic action be carried on in a particular. manner departing from practices heretofore followed in the ordinary electro-deposition of metals upon cylindrical or similar curved surfaces.

In addition, it has been found that it is essential if the shell is to be capable of being readily stripped from the base, and, particularly, if it is to be removed from the base by a depleting action rather than by the stripping action, that is preferred, that the base cylinder be provided with a barrier layer that will protect the base from permanent adhesion of the electro-deposited metal thereto, and will, at the same time, protect the base from the action of the electrolyte tend ing to mar the mirror-like finish, with which the base is provided prior to the electro-deposition thereon of the removable shell.

This invention relates to the production of printing forms, particularly of the type disclosed 5 in my patent just referred to, that have all of the improved characteristics just pointed out.

The base for the form in accordance with the present invention, consists of a base proper, preferably cylindrical in form and an isolating 1v layer or barrier layer surrounding it, or the base itself maybe made of a metal with which the copper shell will not readily or intimately unite, and which is unaffected by repeated subjection to electrolytic action. In either event the outer 1i surface of the isolating layer, or the base itself if no isolating layer is used, is made of an exact predetermined diameter and its surface is provided with a highly polished or mirror-like finish. The highly polished surface is necessary because with '20 my improved plating methods hereinafter set forth any imperfections in the base or isolating layer, as the case may be, will be reproduced in the coating that is subsequently applied electrolytically in accordance with this invention as by 25 the use of an apparatus such as is hereinafter described, as representative of one way of carrying out the process.

The dense uniform shell, in which the printing surface is usually etched and which must be 30 made of an identical thickness at all points lengthwise of the base and around the entire periphery thereof, has a thickness of the order of only .006 inch. Copper is the metal usually employed to form said shell; I have discovered 35 that such a shell, when formed on a; base having a highly polished or mirror-like finish, in accordance with this invention, presents a surface ready for the etching process and that the shell is readily removable and is provided with highly '40 finished outer surface of uniform dimensions and density at all points thereof.

In the production of printing forms of this I character it is further extremely desirable to be .able to applythe outer printing surface rapidly as well as evenly. It has been found that if it is proposed to expedite the deposition by the use of heavy current densities with methods heretofore used'that thedeposlted layer is porous or spongy and is burned rendering it unadapted for the purpose for which it was intended.

In accordance with the prior methods of plating, to avoid this burning action and to secure a satisfactory metal deposition, it has been the practice to use relative small currents with a com- 55 paratively large gap between the cylinder that is to be plated and the electric pole and to carry the plating forward slowly. No effort was directed toward keeping the distance between the cylinder and the cooperating electric pole uniform at all points in order to produce a uniform deposit capable of being used without grinding. A gap of as much as six inches or more has been used in the prior machines, and when plating is carried forward in the usual manner heretofore practiced; it is impossible to provide a uniform thin shell that substantially duplicates'the surface of the base upon which the plating is carried forward, so that when plating is carried in the usual manner the surface must be smoothed and polished before it can be etched, and even then a satisfactory surface may not be secured because of variations in density of various parts of the shell. I have found that by utilizing an electric pole or electrode that generally parallels the surface of the base throughout substantially the entire extent of submersion of said base within the electrolyte. and that by rotating the cylinder, which constitutes the other electric pole or electrode at a relatively high speed of the order of 400 to 800 feet per minute at the cylinder surface I am enabled to use a materially shorter gap of approximately two inches and materially heavier currents than have heretofore been used, such as 1200 amperes, and at the same time to speedily secure a uniform dense deposit that is entirely suited to receive the etched printing surface thereon.

I have also found that it is important in obtaining the necessary uniform thickness and.

density of the shell and smoothness or finish of its outer surface, to maintain a continuous circulation of the electrolyte between the electric pole or electrode and the surface ofthe base so that fresh electrolyte is being continuously brought between said pole and base. preferably secured in this invention by utilizing the cylinder to cause the electrolyte to flow through the gap so that the extent of circulation varies with the speed of rotation of the cylinder, permitting the use of gaps approximately onethird as wide as the gaps heretofore used, while at the same time currents of approximately double the strength of prior current strengths may be utilized without burning. The form and disposition of the stationary pole with respect to the base, and the continuous circulation of electrolyte through the space between said pole and base are of importance in securing the desired uniform density and smoothness, not only when the-coating is applied to the base electrolytically, but these features contribute greatly to the speed with which the coating may be electrolytically removed from the base, if it is desired to employ this procedure in removing theshell, rather than the stripping process that is particularly described in the patent above referred to, or by the acid proces of removal long known in the prior art for removal of zinc lithographic shells. While my improved shell may be removed by suitable acids that will not attack the barrier surface, I have discovered that the removal may be more rapidly, economically, and conveniently effected by a reverse electroyltic action in my, improved apparatus and by my improved plating methods, without This circulation isgreases acids in intaglio printing establishments necessary where acid removal is used.

The primary object of this invention accordingly is to provide novel methods-that will produce or remove the shell of printing forms of the above type for rotary photogravure and like processes in an exceedingly rapid and expeditious manner electrolytically.

A further object of the invention lies in the provision of a. method designed to apply the opter shell or coating of a printing form td a mirrorlike base, such as a cylinder in a uniform manner so that a thin dense shell having an external finish like that of the base is produced that may be readily removed therefrom as by stripping or similar means that will maintain the mirror-like surface of'the base in substantially its original condition after the removal of the outer covering.

Further objects of the invention will appear as a description thereof proceeds with reference to the accompanying drawing illustrating one form of apparatus for practicing the method and in which:

Figure 1 is a transverse sectionalview taken on the plane of the line l-l in Figure 2.

Figure 2 is a longitudinal sectional view taken on the plane indicated by the line 2--2 of Figure Figure 3 is a fragmentary sectional view of the base used in the manufacture of the printing form of" this application.

Like reference characters indicate like parts throughout the several figures.

In the drawing, the numeral ill indicates the base of a. printing form that is provided with suitable supports such as shaft sections projecting herence thereof to such a degree as to injure the mirror-like surface or isolating layer when removing the-sheil by stripping, or electrolytically as will more fully hereinafter appear. Said layer I2 may be of nickel applied in the manner described in my Patent No. 1,831,645, November 10, 1931, or in any other manner resulting in an equivalent deposit. Nickel is very effective in resisting electrolytic action, and for this reason is preferred if the printing surface is to be removed by electrolytic action, as hereinafter described. Or, if desired the isolating layer i2 may be simply or include a coat of wax on any suitable metal, or may be formed by rubbingan oily cloth, or an oxidizing agent over the polished surface of the cylinder constituting the base of the roll. If the cylinder III is made of a material to which the outer printing surface or shell does not readily adhere the layer l2 may be dispensed with. A construction of this kind is described in my copending application 8. N. 146,102 filed November 4, 1926, in which the base is constructed of an iron composition that will readily take a mirror surface polish and that will not readily intimately unite with a coating of copper, the material usually employed to form the printing surface or The isolating or barrier layer, or the outersurface of the base, if no such layer is used, is finished to precisely the diameter required for the printing operation, and given a high polish or mirror-like surface, inasmuch as any irregularities or imperfections therein, even a finger print, will be reproduced in the outer surface of the shell when said shell is completed in accordance with the method and apparatus hereinafterably employed. Said apparatus comprises a tank l3 having a base l4 and sides l5 joined by ends l6 constituting a receptacle open at the top. Disposed in the ends iii of the receptacle just described are supports I! for roller bearings l8 suitably arranged thereon in well known manner.

The supports ll of the base l0 extend through the roller bearings I8 whereby the preferably cylindrical base is rotatably mounted in the end walls of the receptacle. In order to protect the supports ll suitable sleeves l9 and 20 are disposed around said supports. Said sleeves are provided with annular projections 2i and 22 each provided with an opening 23 providing a convenient means for the insertion of an implement to facilitate the removal of the cylinder from the receptacle after the completion of the operation thereupon.

Suitably supported as by brackets 24' secured to the ends l5 of the receptacle is an electric pole or electrode 25 preferably having a straight portion 26 and a curved portion 21 extending away from said straight'portion. As shown'irr Figure 2 the curved portion 21 is of a width at least as great as the length of the cylinder l0 and as shown in this figure and Figure 1, thetop face of the curved portion is spaced substantially equally from the surface of the cylinder forming an annular passage of substantially the same width and length between said surface and the surface of the cylinder. Suitable openings '23 may be provided in the straight portion 26 of the pole 25. Disposed within the tank I3 is an electrolyte 29 that is maintained in any suitable manner at the level shown in Figures 1 and 2 of the drawing. As shown in said figures, this level is suflicient to cover approximately 90 of the surface of the cylindrical form or cylinder when the liquid is at rest. As further shown in Figure 1,

' the curved portion 21 of the pole 25 terminates at a point below the level of the electrolyte. This point is so disposed'that the electrolyte is free to flow over the edge of said pole in a manner presently to 'be described.

In order to rotate the form or cylinder III, a pulley 30 is fixedly secured to one end of one of the shaft sections il thereof. Said pulley 'may be driven from any suitable source of power in well known-manner. The sleeves I5 and 20, roller bearings l8, and-the pulley 30 are held in assembled relation with respect to supports, II by end caps 3| and 32 that are secured to said supports by cap screws 33 or similar means. A wire 34 leading from a suitable source of electric energy is connected to the pole 25. A wire 35 is connected by means of a brush or contact 36 bearing upon the periphery of the annular projection 2| or 22 of the sleeves l9 and 20, serves to establish the cylinder I0 as the other pole of the. electroplating apparatus.

In operation an electrolyte solution, preferably composed of a simple solution of copper sulphate and water of 20 degrees Baum density and brought up to 22 degrees Baum by the addition of sulphuric acid, ora solution of copper sulphate, sulphuric acid and water in proportions cus- 3 tomarily-used by those skilledin the art is placed in the receptacle and maintained at the level indicated in Figure 1. A cylinder to be coated is rotatably mounted in bearings l3. Said cylinder is then caused to rotate at a surface speed of about 400 to 800 feet a minute, though it should be understood that higher speeds may be employed if desired. Relatively great speed is necessary to permit the use of large currents and rapid satisfactory deposition. The flow of electric current is then started, said flow taking place through the pole 25 constituting the anode, the electrolyte 29, the cylinder l0, constituting the cathode, brush 36 and wire 35. Inasmuch as the cylinder I0 is provided with an isolating layer I2 or the cylinder itself is of such character that the copper will not intimately combine therewith, a thin shell-like layer of copper is rapidly disposed upon the cylinder III that maybe removed by stripping or electrically. Its outer surface will be found to conform precisely to the outer surface of the cylinder upon which it is deposited.

It is extremely important that thisshell-like deposit be of a uniform thickness from end to end of the cylinder and around the entire periphery thereof for the' best results in the printing operation. This desirable uniformity is brought about by providinga pole, constituting the anode, that extends from end to end of the cylinder but in spaced relation thereto, and that is curved so that l the nearest surface of the anode is substantially equi-distant from the adjacent cylinder at all points beneath the surface of the electrolyte. Contributing to the uniformity of the deposit is the disposition of the tip of the anode below the surface of the electrolyte solution so that the rotating base will cause the solution to move over said tip.

It will beobserved that by this arrangement when. the cylinder is rotated at high speed, the electrolyte will be carried over and will circulate through the channel provided between the inner surface of the anode and the adjacent surface of the cylinder. That is, capillary attraction and friction will cause the electrolyte to move with the surface of the cylinder in the direction of the arrows as indicated in Figure 1. Said electrolyte may be discharged over the top of the straight tion between the anode and the cylinder is being continually changed in the manner just described.

In this way the uniform characteristics of the electrolyte are maintained throughout substantially all portions of the tank by the agitation resulting from the rapid rotation of the cylinder and there is no opportunity for a decided change in the character of the electrolyte that is immedi ately under the influence of the electric current passing from the anode to the cylinder constituting the cathode. 'Imthis way a thin layer of uniform thickness of about 0.005 to 0.008 of an inch and of heavy density from end to end of the cylinder and around the entire periphery thereof and having a smooth outer printing surface without the necessity for further polishing operations is secured At the same time the relatively rapid rotation of thecylinder not only keeps the electrolyte in constant agitation but said cylinder serves to continuou'sly draw a fresh supply of electrolyte from 5 through the openings 28' orover the top edge of the anode.

The curving of the stationary electric pole 25 in substantial parallelism with the surface of the cylinder that is below the level of the electrolyte,

10' the extension of said pole laterally from end to end of the cylinder, the continuous change of the electrolyte solution between the cylinder and the stationary pole, the high speed of rotation of the cylinder and the heavy applied currents are the 15 factors that result in the perfectly uniform smooth deposit of desirable quality and density on the cylinder required for the production of a thoroughly practical printing form for rotogravure work and that cause the coating to be go removed and deposited evenly on the stationary pole when the direction of current flow is reversed.

The coating or shell deposited as above pointed out on a base with a proper barrier or isolating surface or layer against intimate union maybe 25 removed by a simple stripping of the shell from the cylinder after it has served its purpose. This may be brought about by first separating a strip of deposited metal, which covers the ends of the cylinder withdiminishing thickness toward the 30 axis of the cylinder, tearing such strip to the cylinder surface and then across the cylinder thus and then stripping the shell from the cylinder.

I have discovered that proper isolating layers act as barriers against intimate union and the 35 strong breaking down reverse electrolytic action ,under the influence of imposed substantial extraneous electro-depositing voltages sufficiently to prevent destruction of the smooth or mirror-like base surfaces essential for the manufacture of a 40 printing form. Accordingly if desired, the outer shell can be removed electrically by mounting the cylinder in the apparatus above described in the same way in which it is mounted when the printing deposit or shell is formed. In order to remove 45 the coating, however, the direction of flow of the current is reversed, and the curved pole or electrode disposed in the electrolyte becomes the cathode. The removal of this shell can be expedited by rotating the cylinder at a high rate of 50 speed while a relativelyheavy current is flowing in the opposite direction. The minute etched depressions in the shell, provided to form the printing surface, contribute to the speed of removal of the coating under this reverse action of the 55 apparatus. The electrolyte,- entering into said depressions, adds to the effectiveness of the action ofv said electrolyte without adverse effects upon the smooth surface of the barrier or isolating layer beneath the coating, since after the portions of thecoating that are thinnest due to the etching of the surface are removed exposing the smooth surface of the base, the removal of the remainder of the coating continues without causing a roughening of said mirror-like surface, said surface being formed of a metal that is impervio'us to electrolytic action as will be readily understood.

The very rapid movement of the cylinder is found to add greatly to the effectiveness of the 70 apparatus in removing the shell in this manner,

so that the action of the isolating layer as a barrier against electrolytic action under substantial current flows, together with the fact that a substantially uniform minute removal is ef- 75 fected by each revolution of the rotating pole,

shell, as was the practice prior to the invention H disclosed in the patent above referred to, it was difiicult to remove the shell electrolytically with,- out destroying the desired smooth surface of the base because the action of the electrolyte in breaking down such union affected said smooth surface producing a roughness or slight pitting of said surface that renders it impracticable to again use the base, without burnishing, for the reception of a new shell. Such burnishing is laborious and reduces the size of the base. By the method disclosed in this application the metal is removed rapidly and evenly with the result that portions of the baseopposite to the deepest etched depressions in the shell are brought in contact with the electrolyte and subject to the electrolytic action, before most portions of the base are similarly affected. If an intimate union exists between the shell and the base the portions of the base thus exposed tend to become roughened. However, as proposed in this application, no such union exists. Accordingly it has been found that the shell may be removed electrolytically without destroying the mirror-like surface of the base though it is not initially of identical thickness at all points. The electrolytic action does not readily affect the base at the points-first exposed because its highly polished surface is resistant to the electrolytic action and furthermore because of the absence of the above referred to intimate union between the metal of said base and the metal of the shell. For the latter reason it is desirable not to effect an intimate union between the base and coating, though said coating may be removed electrolytically, even if such union is formed by the process and apparatus of this application. This application is a division of my copending case Ser. No. 270,367 filed April 16, 1928.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims ratherthan by' the foregoing de- A scription, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is: 1. A printing cylinder consisting of a base provided with a barrier layer of nickel polished to a mirror-like finish, and a' layer of copper electrodeposited on said base, said layer having a thickness not materially greater than just sufflcient to permit the etching therein of the print- .ing surface in the copper layer. I

2. A rotary intaglio printing form comprising a metallic cylinder provided with a thick covering layer of nickel having a. smooth polished surface, and an outer layer of electrolytically deposited copper, said outer layer having a thickness sufficient for one etching only.

3. The method of providing a printing cylinder with a copper layer suitable for etching, which consists in providing a cylindrical base with a passivating layer of nickel having a smooth-polished finish resistant to the action of the electrolyte o! a copper electroplating apparatus, immersing said cylinder in the electrolyte o! a copper electroplating apparatus. rotating said cylinder on a substantially horizontal axis through the electrolyte at a relatively high surface speed in manner to cause a continual circulation of the electrolyte during the deposition of the copper and to allow or a voltage which will insure a high current density, and causing current of approximately two hundred amperes per square foot of cylinder immersed in the electrolyte to flow until a dense non-porous layer of copper of sufflcient thickness is produced without burning.

4. The method of providing a printing cylinder with a copper layer suitable for etching; wnichconsistsinprovidinsacylindricalbcse with a passivating layer '0! nickel having a smooth-polished finish resistant to the action or the electrolyte of a copper electroplating apparatus, immersing said cylinder in the electrolyte or a copper electroplating apparatus, rotating said cylinder through the copper electrolyte and simultaneously causing a constant circulation of the electrolytethrough which current is flowing so as to allow of .a voltage which will insure a high current density, and causing current of approximately two hundred amperes per square foot of cylinder immersed in theelectrolyte to flow until a dense non-porous layer of copper of suillcient thickness is produced without burning.

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