US1918627A - Apparatus for producing printing forms - Google Patents

Description

July 18, 1933 E. S. BALLARD APPARATUS FOR PRODUCING PRINTING FORMS Filed April 16, 1928 Patented Jul 18; 1933 UNITED STATES PATENT OFFICE ERNEST S. BALLABID, OI OAKLAND, CALIFORNIA, ASSIGNOB, BY MIENE ASSIGNMENTS, TO STANDARD PROCESS CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION 01' DELAWARE APPARATUS FOR PRODUCING PRINTING FORMS Application filed April 16,

This invention relates to printing forms and methods and apparatus for produclng printing forms for use particularly in rotary photogravure and like processes.

In the manufacture of such forms it is customary to provide a base structure, usually in the form of a cylinder, and to provlde a coating thereon of copper applied to the cylinder by electro-deposition. The etched printing surface is formed in'this copper coating or shell that surrounds the cylindrlcal base. After the printing form has been used it has been the practice to remove the copper shell or coating by grinding or by the use of acid. In my Patent No. 1,643,046 granted September 20, 1927, there is disclosed one way of producing a printing form in which the printing surface or shell can be removed by stripping the shell from the base there shown. The method disclosed in this patent provides an extremely simple and practicable method of removing the shell after it has served its purpose.

This invention relates to the production of printing forms particularly of the type disclosed in my patent just referred to. It is essential in the production of such forms that the base for the form consist of a base proper, preferably cylindrical in form and an isolating layer or barrier layer surrounding, or the base itself may be made of a metal with which the copper shell will not readily or intimately unite. In eitherevent the outer surface of the isolating layer or the base itself, if noisolating layer is used, is made of a predetermined diameter and its surface is provided with a highly polished or mirror finish. The highly polished surface is necessary because with 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 the process and by the use of an apparatus such as is hereinafter described.

The shell in which the printing surface is usually etched must be made of an identical thickness at all points lengthwise of the base and around the entire periphery thereof.

The shell is usually quite thin and copper is 1928. Serial No. 270,367.

the metal usually employed to form said ished or mirror finish in accordance with my invention will result in a printing form ready for the etching process that has a readily removable shell with highly finished outer surface of uniform dimensions at all points thereof. This invention relates particularly to the formation of the shell upon which the printing surface is to be formed having the characteristics just stated.

In the production of a printing form of this character it is extremely desirable to be able to apply the outer printing surface rapidly as well as evenly. It has been found that ifit is proposed to expedite the depositionby the use of heavy current densities with methods and apparatus'heretofore used that the deposited layer is porous or spongy and is burned rendering it unadapted for the purpose for which it is 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 comparatively large gap be tween the roll being plated and the electrode and to carry the plating forward .slowly.

No effort was directed toward keeping this distance accurately uniform 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 and, materially heavier currents than have heretofore been used, and at the same time to speedily secure a uniform dense deposit that is entirely suited to receive the etched printing surface thereon.

Ihave also found that it is important in obtaining the necessary uniform thickness of the shell and smoothness or finish of its outer surface, to maintain a continuous circulation of the electrolyte between the electric pole or tinuous circulation of electrolyte through the.

space between said pole and base are of importance in securingthe desired uniformity 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 thisprocedure in re'moving the shell rather than the stripping process that is particularly described in the patent above referred to, or by the acid process of removal long known in the prior'art for removal of ZlIlC lithographic shells. While my improved shellmay 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 electrolytic action in my improved apparatus and by my improved plating methods, without destroy- 1ng the InllIOI surface of the base,'permitting ,use of a single apparatus for plating and deplating and obviating the necessity for handling comparatively large quantities of strong acids in intaglio printing establishment's n ecessary where acid removal is used.

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

A further object of the invention is a method and apparatus designed to apply the outer shell .or coating of a printing form to a mirror-like base such as a cylinder in a unlform manner so that a thin 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 $11;

basein substantially its original condition after the removal of the outer covering.

Further objects of the inventidn will appear as a description thereof proceeds with reference to the accompanying drawing in which:

Figure 1 is a transverse sectional View taken on the plane of the line 11 in Figure 2.

Figure. 2 is a longitudinal sectional view taken on the plane indicated by the line 22 of Figure 1:

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 10 indicates the base of a printing form that is provided with suitable supports such as shaft sections 11 projecting in opposite directions from the ends thereof. -Preferably the base 10 is hollow and is made of copper, though any other suitable material may be used. If copper is used an isolating or barrier layer 12 is applied to the outer surface of the cylinder to prevent an intimate union of the electrically deposited outer layer or shell or adherence thereof to such a degree as to injure the mirror-like surface of base or isolating layer when removing the shell by stripping or electrolytically as will more fully hereinafter appear. Said layer 12 may be of nickel applied in the manner described in my copending application Serial No. 222,505 filed September 28, 1927. 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 12 may be simply a coat of wax on any suitable metal or may be formed by rubbing an oily cloth or an oxidizing agent over the polished surface of the cylinder constituting the base of the roll. If the cylinder 10 is made of a material to which the outer printing surface or shell does not readily adhere the layer 12 may be dispensed with. A construction of this kind is described in my copending application Serial No. 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 usuallyl employed to form the printing surface or s ell.

The isolating or barrier layer, or the outer surface of the base, if no such layer is used, is furnished 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 afinger print, will be reproduced in the outer surface of the shell when said shell is completed in accordance with the method and apparatus hereinafter described, indicating the extreme uniformity of the coating applied by said method and apparatus.

In order to apply the outer coating or shell to the base 10, with or without the isolating layer 12, an apparatus shown in Figures 1 and 2 is preferably employed. Said apparatus comprises a tank 13 having a base 14 and sides 15 joined'by ends 16-constituting a receptacle open at the top. Dis posed in the ends 16 of the receptacle just described are supports 17 for-roller bearings 18 suitably arrangedthereon in well known manner.

The supports 11 of the baselO extend through the roller bearings 18 whereby the preferably cylindrical base is rotatably mounted in the end walls of the receptacle. In order to protect the supports 11 suitable sleeves 19 and 20 are disposed around said supports. Said sleeves are provided with annular projections 21 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 fromthe receptacle after the completion of the operation thereupon.

Suitably supported as by brackets 24' secured to the ends 16 of the receptacle is an electric pole or electrode 25 preferably having a straight portion 26 and a curved portion 27 extending away from said straight portion. As shown in Figure 2 the curved portion 27 is of a width at least as great as the length of the cylinder 1.0 and as shown in this figure and Figure 1, the top 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 28 may be provided'in the straight portion 26 of the pole 25. Disposed within the tank 13 is an electrolyte 29 that is mainained in any suitable manner at the level shown in Figures 1 and 2 of the draw.- ing. As shown in said figures, this level is sufficient 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 27 of the pole 25 termin tes 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 10,a pulley 30 is fixedly secured to one end of one of the shaft sections 11 thereof. Said pulley may be driven from any suitable source of power in well known manner. The sleeves 19 and 20, roller bearings 18, and the pulley 30 are held in assembled relationwith respect to supports 11 by end caps 31 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 supply 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 '21 or 22 of the sleeve 19 and 20, serves to establish the cylinder 10 as the other pole of the electro-plating 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, or a solution of copper sulphate, sulphuric acid and water in proportions customarily used by those skilled in the artis placed in the receptacle and maintained at the level indicated in Figure 1. A cylinder to be coated is rotatably mounted in bearings 18. Said cylinder is then caused to rotate at a surface speed of about 350 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 10, constituting the cathode. brush 36 and wire 35. Inasmuch as the cylinder 10 is provided with an isolating layer 12 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 10 that may be 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 this shell-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 providing a pole, constituting the anode, that extends from end to end of the cylinder but in spaced relation thereto, and that is curved so that the nearest surface of the anode 13 substantially equi-distant from the adjacent cylinder at all points beneath the surface of the electrolyte. Contributing to the uniforinity of the deposit is the disposition of the tip of the anode below the surface of the electrolyte solution so that the rota'tmg base will cause the solution to move over said tip.

It will be observed that by this arrangement when the cylinder is rotated at high speed, the electrolyte will be carried and will c1rculate 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 portion 26 of the anode 25, or it may be discharged through openings 28 provided in' said portion of the anode as may be desired. It will be observed that by this arrangement the electrolyte will not only be kept in continuousagitation by the rotation of the cylinder, but that the electrolyte solution between the anode and the cylinder is being continually changed in the manner just described. In this way the 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 immediately under the influence of the electric current passing from the anode to the cylinder constituting the cathode. In this 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 the cylinder not only keeps the elec trolyte in constant agitation but said cylinder serves to continuously draw a fresh supply of electrolyte from the body of the solution over the right hand edge of the cathode, viewing Figure 1, maintaining this electrolyte between the anode and the cylinder for only a short time when it is discharged through the openings 28 or over 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 the extension of said pole later-' ally from end to end of the cylinder and the continuous change of, the electrolyte solution between the cylinder and the stationary pole are the factors that resultin the perfectly uniform smooth deposit of desirable quality and density on the cylinder required for the production of a thoroughly practical printing fofm for rotogravure work and that cause the coating to be 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 may be removed by a simple stripping of the shell from the cylinder after it has served its purpose. This may be brought about by forming a longitudinal slit from end to end of the cylinder and then simply stripping the shell from the cylinder. I have discovered that proper isolating layers act as barriers against intimate union and the strong breaking down reverse electrolytic action under the influence of imposed substantial extraneous electro-depositing voltages suiiiciently to prevent destruction of the smooth or mirror like base surfaces esdisposed in the electrolyte becomes the cath- I ode. The removal of this shell can be expedited by rotating the cylinder at a high rate of speed while a relatively heavy 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 apparatus. The electrolyte, entering into said depressions, adds to the effectiveness of the action of said electrolyte without adverse effects upon the 'smooth surface of the barrier or lsolating layer beneath the coating since after the portions of the coating 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 impervious 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 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 effected by each revolution of the rotating pole, prevents destruction of the essential polished base surface during the reverse electrolytic action. It has been found also that the removal of the shell electrolytically is facilitated by the fact that no intimatv union exists between the shell and the highly polished base. When an intimate union is effected between the base and the printing shell, as was the practice prior to t e invention disclosed in the patent above referred to, it was diflicult to remove the shell electrolytically without destroying the desired smooth surface of the base because the action ofthe 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 disclosedin this application the metal is removed rapidly and evenly with the result that port ons of the base opposite 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 de- .-;tro ving 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.

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 rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What I claim as my invention is 1. An apparatus for forming or removing a shell-like printing surface on or from a cylindrical base, comprising a receptacle, a cylindrical base constituting an electric pole, means'to rotatably support said cylindrical base in said receptacle with a portion thereof extending beneath an electrolyte solution, a plate constituting an electric pole and having a curved portion and a continuous uninterrupted surface extending substantiall parallel to and coextensive with the sur ace of that portion of the cylindrical base that is disposed beneath the level of the electrolyte and terminating below said surface at the side of the base that moves downwardly upon rotation thereof so that rotation of the base a shell-like printing surface on or from a cylindrical base comprising a receptacle provided with means to maintain an electrolyte at a given level, means to support said cylindrical base within said receptacle with approximately one-fourth of the surface thereof extending beneath said level, a plate coextensive in length with the length of said base supported in said receptacle having a curved portion extending nninterruptedly at a given level, means to rotatably support said cylindrical base in said receptacle with approximately one-fourth of the surface of said base extending beneath said level, an electric pole comprising a plate coextensive in length with the length of said base and extending beneath said level and having a portion curved so that its surface adjacent to said base is substantially parallel to the portion of the surface of the base that is beneath said level, one edge of said plate terminating beneath said level at the side of the base that moves downwardly upon rotation thereof, and means to rotate said base whereby the electrolyte is caused to circulate over said edge and through the space between said base and plate.

4. An apparatus for forming or removing a shell-like printing surface on or from a cylindrical base comprising a receptacle provided with means to maintain an electrolyte at a given level, means to support a cylindrical base in said receptacle with approximately one-fourth of the surface thereof extending beneath said level, a plate coextensive in length with the length of said base supported in said receptacle above said level and having a portion thereof extending from said supporting portion beneath said level, the portion of the plate extending beneath said level being curved so that it extends uninterruptedly in parallel relation with the surface of said base, said last named portion having an edge that terminates below said'level, and means to rotate said base through said electrolyte at a relatively high speed to facilitate the flow of electrolyte continuously over said edge and through the space between said base and the plate, and electrical connections arranged so that the plate will constitute one of the poles and said cylindrical base will constitute the other.

' 5. An apparatus for electro-plating rintof said base will cause circulation of electrolyte over said edge and through the space between said base and plate, and means to apply relatively heavy external electrodepositing voltages across said space whereby a dense uniform deposit having an external smoothness reproducing that of the uncoated base is rapidly produced.

ERNEST S. BALLARD.

Images