US2670326A - Producing curved electrotypes - Google Patents

Description

Feb. 23, 1954 w. BUNGAY PRODUCING CURVED ELECTROTYPES v v 3 Sheets-Sheet 1 Filed Sept. 20, 1950 HEAT& PRESSURE a 4 D l m l H #M 5 M 1,

3 L28 LUT INVENTOR. GEORGE W BUIYGAY BY ATTORNEYS.

Feb. 23, 1954 G. w. BUNGAY PRODUCING CURVED ELECTROTYPES 3 Sheets-Sheet 2 Filed Sept. 20, 1950 INVENTOR. GL'OIPGE M BUNGAY BY I I )i ATTORNEYS.

Feb. 23, 1954. e. w. BUNGAY PRODUCING CURVED ELECTROTYPES 3 Sheets-Sheet 5 Filed Sept. 20, 1950 INVENTOR. 650x 5 h./ BUNG Y )1 By *Qw q 14 TTORNE Y5.

Patented Feb. 23, 1954 PRODUCING CURVED ELECTROTYPES- George W. Bungay, New York, N. Y., asssignor to Electrographic Corporation, New York, N. Y., a corporation of Delaware Application September 20, 1950, Serial No. 185,792

6 Claims.

The present invention relates to a process of preparing cylindrically curved electrotypes for letterpressprinting.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the processes and steps pointed out in the appended claims.

The invention consists in the novel processes, arrangements, steps and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate the preferred manner of carrying out the present invention.

' Of thedrawings:

Figure 1 is a schematic view showing the formation of a plastic electrotypers mold from a flat, original letterpress printing plate, such as a photoengraving I Figure 2 is a schematic view showing the fact of the mold prepared inaccordance with the step shown in Figure 1 Figure 3 is a plan view on a reduced scale showing a plurality of such molds after they have been trimmed and joined together along their adjacent side edges, with the several plates in correct registered position;

Figure 4 is a detailed sectional view taken on the line 4-t of Figure 3 and showing the joint has been cylindrically curved and while it is supported in a cylindrical case;

Figure 6 is a developed view showing the face of the electrodeposited shell as its longitudinal edges are trimmed therefrom;

Figure '7 is an end view and Figure 8 a side view schematically showing the step of trimming of the sid edges from the electrodeposited' shell; Figure 9 is a sectional view showing the shell positioned within a rotatable casting drum to be rotated at a relatively high speed for the centrifugal casting of backing metal on the shell;

Figure 10 is a longitudinalview through the casting drum of Figure 9;

' Figure 11 is a fragmentary detailed sectional view showing a portion of an end of the casting drum with the shell and, backing metal in position as cast therein;

Figure 12 is a, perspective view showing a cylinder, including a. plurality of th plates' as cast,

andasit is;removed from-the casting cylinder;

Figure 13 is a perspective view of a single fragmentary curved plate cut from the cylinder shown in Figure 12; and

Figure 14 is a sectional view through one of the plates, such as that shown in Figure 13, after the plate has been finished and is ready to be positioned on the rotary printing press for printing.

The present invention has for its object the provision of a novel and improved process of forming cylindrically-curved electrotypes from flat letterpress printing plates, which electrotypes are of improved quality, may be more economically produced than heretofore and may be made-ready for printing with a minimum of preparatory work after they are delivered to the press for plating. A further object of the invention is the provision of a novel and improved process of forming high quality cylindricallycurved electrotypes which will accurately register with each other and with the other printing plates of the set. The invention further provides an improved process of forming curved electrotypes in which the metal of the plate is initially formed as a cylindrically-curved member.

Heretofore it has been proposed to produce cylindrically curved electrotypes by many difierent processes but these prior processes are either impractical in commercial operation or produce imperfect plates or plates which require a great amount of expensive manipulation, such as registering and make-ready after the casting and finishing operations have been completed and the plates are delivered to the press for the plating of the cylinders.

The conventional manner of forming cylindrically curved electrotypes is to produce a fiat electrotype and then'subject it to a curving operation by which the flat plate is curved to the desired degree, after which the plate may be finished and is made-ready and positioned on the press. In such a process, the curving of the plate results in uneven stretching of the plate, and the plates of a set of color plates are likely to stretch unequally with respectto the other plates of the set, thereby destroying the possibility of accurate color registration. Furthermore, during the curving operation, th .printing surface of the plate is often damaged, the printing surface becomes uneven so that extensive makeready treatment is required, and often, the resulting cylindrically curved plate is not of the desired diameter so that it is not capable of'being securely seated. on the printing cylinder.

According to another process which has not been commercially used to any extent,fiat electrotype shells are positioned within a cylindrical drum and held therein by clamping strips, sevcral such shells being arranged to form a substantially complete surface on the interior of the drum. The drum is then rapidly rotated, and while so rotated molten backing metal is poured within the drum and allowed to congeal, resulting in the formation of backed cylindrical plates which are thereafter removed from the cylinder and finished. In this process the positioning of the several shells within the drum requires the use of separate clamping members between the adjacent edges of each pair of shells, the removal of the plates from the drum is relatively slow and difficult, and the plates produced are likely to be imperfect due to the relatively great expansion of the copper shell at the time the molten backing metal is poured into contact with the rotating shell. Furthermore with such a process it is virtually impossible to produce a plate which is accurately registered, or to produce the several plates of a color printing set which will accurately register with each other.

According to another prior process, the several shells are curved to approximately the desired diameter after their edges have been trimmed, and a narrow strip, such as a strip of iron, having parallel channels along its opposite edges is used to bind the adjacent edges of two shells together,

a sufficient number of shells with sufficiently wide margins being provided so that they may be joined into a cylinder which is of the same diameter as the interior of the drum in which the shells are to be positioned by backing with molten metal while being subjected to centrifugal force.

' This process is disadvantageous inasmuch as it is relatively difficult to accurately register the shells with respect to each other, there is considerable danger of scratching the delicate surface of the shells as they are inserted into the drum in which they are to be backed, and the strips temporarily securing the shells together interfere with sawing the plates apart and necessitate frequent resharpening of the saws.-

The various disadvantages of the foregoing and other prior processes, are avoided by the present invention which provides a simple, expeditious and reliable process of producing superior, cylindrically-curved electrotypes which are ready for printing and require only a minimum of finishing and makeready.

The accompanying drawings illustrate schematically, and in some detail, the various steps involved in producing cylindrically curved electrotypes from a hat letter press plate such as a photoengraved printing plate. In accordance with the preferred manner of carrying out the present invention, a plastic electrotypers mold is formed by heat and pressure from an original relief or letterpress plate I9 such as a photoengravi s.

As is usual in the formation of such molds, the

plate I0 is laid on the heated platen I4 of a hydraulic press, the plate is surrounded by the usual bearers i2 and a sheet of the desired thickness and grade of thermoplastic material [6 is laid 'over the face of the plate ill and the bearers l2,

after which the upper platen I8 is moved to exert even pressure on the sheet (6 of thermoplastic material. The pressure and heat are continued for a sufficient length of time to properly form the thermoplastic mold. While a variety of thermoplastic materials may be used for the sheet l6.

I prefer to use material such as a vinyl acetate- 4 vinyl chloride copolymer of a grade commercially used in the trade for this purpose.

Figure 2 is a plan view showing the principal features of the mold 20 produced by the step illustrated in Figure 1. As shown, the mold 26 has depressions 22 formed in its face corresponding to the printing areas of the original plate Iii. The mold is also provided with a plurality of spaced apart register marks 25 which serve for the subsequent registration of the several molds with respect to each other, and may be used for eventually checking the register of the finished cylindrically-curved plates. These register marks 24 need not be sufficiently deep in the mold 20 to form printing surfaces, and may be located within or without the general printing area of the plate. Preferably, the register m rks are uniformly positioned in any given series of plates, and where possible it is a convenience to have the register marks on all of the plates being made similarly positioned.

The mold 20 after it has been removed from the plate It is trimmed to form square corners, and the trimming is illustratively carried out along the dot-dash lines 26 which usually pass through the depressions 28 caused by the bearers l2. The trim lines 26 have a definite predetermined relation to the register points 2 so as to be at right angles to each other, and each of the molds 28 will preferably be of identical size with the other molds 25!.

In the event that it is impossible to provide for this identical relation between the trim lines and the register points 24, the molds 20 may be made of different width, but the molds are trimmed at the top and bottom so that they are of uniform length and have their top and bottom edges uniformly spaced with respect to the register points, and have their side edges parallel to each other.

When a plurality of the molds have been formed and trimmed as described, the molds are assembled on a flat surface with the upper series of register points 24 in accurate alignment with each other and with the lower series of register points correspondingly aligned. If the molds have been properly trimmed the upper edges 39 of the molds will be accurately aligned with each other as will the lower edges 32.

Correspondingly, if the side edges 34 of the molds have been accurately trimmed square with respect to the top and bottom edges, the side edges of twoadjacent molds 20 will accurately contact with each other throughout their length. However, if there is any error in the trimming, the alignment of the register marks 2 from one mold to the next is used as the controlling guide and the errors will be compensated for in a later stage of the process.

With the molds securely held in accurate alignment, as shown in Figure 3, the molds are joined together along their adjacent edges, and for this purpose a strip 36 is laid over the abutting edges 34, and is securely fastened to the narrow margins of the two molds 20. The strip 36 is of material which may be firmly bonded to the material of which the molds 20 are made, and is preferably of the same material as the mold material.

Where convenient, the strip 36 may be heatsealed to the molds 20 along parallel line 38 throughout the length of the strip 36, as by electronic heat sealing, or the strip 36 may be secured by means of suitable adhesive- When thus assembled and joined together a plurality of the molds form a. relativelyv long. composite mold which are approximately by /2".

actuate which is in all cases longer than the circumference of the plated printing cylinder of which they are to form a part.

As purely illustrative of the dimensions which are commonly found useful, the following data is 'given on the assumption that the plates are to be printed on a cylinder which has a printing diameter of 14.3" or approximately 45" in circumference, and is adapted to print four pages each 10" wide on each revolution, from plates For producing such plates the molds may be approximately 15 by 17 each, and three such molds would be joined together, as shown in Figure 3, the overall length of this assembly being 46 or slightly greater than the printing circumference of the final plate cylinder.

Figure 5 schematically illustrates the electrodeposition of an electrotypers shell on the assembled molds 20. As shown in Figure 5, there is provided an electrotypers case 40 which is almost a complete cylinder and is provided at its ends with suitable means 42 for engaging and holding the ends of the assembled molds 20, so that they may be retained therein during the electrodeposition of the shell.

The assembled molds are positioned within the case 40 with their design face toward the interior or on the concave side of the cylindrically bent mold. Preferably the case 40 is formed with a gap 44 of about 10 extent and has a slightly larger diameter than the diameter of the eventual printing cylinder surface. Within the case, and preferably centrally thereof, is located anode 46 from which copper or other metal is derived for the electrodeposition of the shell.

The anode 40 and the cathode face of the mold 40 are suitably connected to a source of direct current and both are immersed in a conventional electroplating bath for the deposition of metal on the face of the molds 20 which have been suitably treated, as by silvering, to render it electrically conductive, the conductive layer extending over the entire face of the mold as well as over the joint strips 36.

After the shell has been deposited to the desired thickness, which is generally from .005 to .020", the case 40 is removed from the electrodepositing bath and the mold with its adherent shell is removed from the case 40. The mold and shell are then separated from each other, care being taken to avoid excessive bending of the shell and damage to its exterior surface, thereby insuring that the shell retains substantially its almost cylindrical shape.

Figure 6.0f the drawing ,is a developed-view showing the face of the electrodeposited shell 50 after it has been removed from its mold 40, which shell is an accurate reproduction of the mold.

The shell 50 is then trimmed so as to remove the rough edges of the electrodeposited metal and so as to reduce the width to the final dimension desired for the plates. The ends of the shell are likewise trimmed at right angles to the curved edges, care being taken that the total remaining length of the shell 50 is somewhat greater, preferably from to 2", than the circumference of the printing cylinder eventually to be used.

For the purpose of trimming the side edges of the shell, the substantially cylindrical shell 50 is positioned on a drum 54 of somewhat smaller diameter and provided with spaced apart rims 56 at its ends. The outer faces of these spaced apart rims cooperate with shearing discs 58 to form a pair of shear cutters which will trim the side edges of the plate to thedesired width as the drum 54 is rotated and as the cutter members 56 and 58 roll in contact with each other. They shear off the narrow metal strips 60 which constitute the excess width of the plate and usually have fairly rough edges. Thereafter the ends 62 are trimmed square along the dot-dash lines 64.

The interior face of the shell is then suitably fluxed and the shell is contracted below the diameter which it will'have after it has been formed into a printing surface. The contracted shell is positioned within a' casting drum 68, the interior surface of which is finished to the correct diameterof the eventual printing surface, which in the illustrative case is 14.3".

The drum B8 is preferably in the form of a hollow steel cylinder of sufficient thickness to have the necessary mechanical strength, and is provided'with enlarged end rims '10 which oooperate with the supporting rollers 12 by which the drum 68 is to be rotatably supported and driven. The drum is held down against the rollers 12 by means of the roller 14'. The mounting of the drum 68 is such that it may be rotated at a relatively high speed, preferably such as 200 to 400 R. P. M. and suflicient to generate a centrifugal force in excess of 100 g. on the backing metal and shell.

Drum 68 is provided at its ends with removable rings which serve not only to retain the shell 50 in position for casting of the backing metal, but also serve as dams during the casting operation,v and prevent the molten backing metal from flow-- ing out of the drum as the drum is rotated. Figure 11 shows in detail the cross sectional shape of the ring 18, the external diameter of the ring being the same as the internal diameter of the drum 68. Each of the rings 18, .on its inner face, is provided with a small radially extending surface of slightly greater width than the thickness of the shell 50 which surface joins a bevelled surface 82 and then another radial surface 84, the radial extent of the surface 82 and 84 preferably being two or three times the thick ness of the backed plate to be formed. Suitable.

meansare provided for securing the rings 18 in position with the ends of the drum while providing for their ready removal and for this purpose set screws 86 maybe threaded in the end rims I0 and maybe turned to engage the outer surface ,of the corresponding ring 18.

As shown in Figures 10 and 11, the rings I8 are spaced from each other a distance such that. the width of the shell 50 causes it to be in substantial engagement with the radial surface, 80,,and the bevelled portions 82 serve to prevent collapse of the cylindrical'shell 50 as it is inserted into the drum 88 as well as during the beginning of the rotation of the drum 68 and prior to the time the centrifugal force fully expands the shell 50.

As shown in Figure 9, the drum is to be rotated in a clockwise direction and the ends of the shell 50 are overlapped so that the leading edge of the shell overlies the trailing edge, the ends overlapping for a considerable distance.

As rotation of the drum 68 begins and continues at an accelerated rate, the shell expands until it is held by centrifugal force in firm contact with the interior surface of the drum 68. When the desired speed of rotation has been attained, the proper quantity of molten backing metal, such as a lead alloy, is introduced into the drum and is poured into the peripheral space between the end rings I8. The metal flows and distributes ts lf h erm r to e rlihd ieel mess she rapidly eee ed b th heat eh heel into mess of th d um 68 th rehrden e layer of. backing me al 90 adhe nt. en t e back s d oi the shell so. 7

As soon as the metal 90 has congealed, the to: e of the rum he is s eeped! one oi the nd. -18 is reme d. rom he r m and the east y n c i ing h shell 50 and back ng 91h m y be i h ewn xia ly irem th d um. in h condition shown in Figure 12 of the elrz wings,

There f h y nderis ut ar e ens' paral: lel axially extending lines so as to separate the three pri ng lates fr m eeeh eth r. Th s 7 preferably carried out by sawing the. plate along parallel lines so that the sawed-apart plates are only slightly lon er than is desi ed f r fini hed plate- 'herebyi th e separate x ih drically curved plates are nredueed; one oi which. 95, is shown in Figure 13. The plates 05 are then finished along their four edges, as by he'velling. along the edges 05, as well as along the curved d es, so that all four ev l ed ed es bee he desired accurate relation tqthe register marks 24 appearing on the face of'the plate.

When so finished, each Plate is ready to be positioned on the plate cylinder of the printing press, accurately conforms to the-surface of the plate. cylinder, and may beclarnped' to. the plate cylinder by the usual plate clamps and without I the elaborate. st ps ueu r nee e to.- pesitieni plate n t e cylinder in accur t r gister fo printing.

It will be noted that the plate shown in Figure.

14 is u s entiauy equ l in extjen neua ter circumference of the cylinder suflicientallowance being made for engagement of the usual plate clips with the beveleq edges 96. However, no additional allowance needbe'made for variably positioning the plate register, as the process of preparingthe plates hasiinsured that they will lie in predetermined'registering position, Where s h a t e lin i el. pl tes-are to. b pr duced, the required Width. of the'strips 36, the Overlap. of the end of e midi ane'the' va ieus. trimming requirements at difierent'stagesof the process usually prevent the production] of more than three p ates from a r i dri ally haelse shelLand. at times it may be desirable to fill out the len th o e meld 20. by the. jo in of. narrow piece of the mold material.

The invention in its broaderaspects'is not limited to the specific processes and steps shown and described but departuresmay bemade there,v from within the. scope of the accompanying claims without departing from'the principles of the invention andwithout sacrificingits chic: advantages.

l eim is:

1-,. Anm ess oil ter ains. ey indrieellr e r ed electrotypes which comprises molding a plurality ei fle ible elee e he molds from ne or m ile minin p ates to be dupl e d as curved e ee retyn s. j in n said molds to ether al ne adjacen d es or s arat p eylindriealli' curving said molds w h. e desi .s ria e. o th m l s as, t e n a e su ac el t e espositns emetel. he on the. con av surf e h mol tripp n t sh l from th m lds. fe m ns t e she int a cylinder of the de ired d ame era kin the sh l, d s r g, e backed. he l nto p uralityo lindr cal. lates- 2. A p ee ss as aimed in eleim. 1 in which nds. of the. j ined molds ar spaced a rt. as the s l s terme th ends of the shell. are erlap ed. s the she eached t melt metal hi e the. she l s rapidl otated on. ts. axis.

A p oces as c aim d n claim 2. n. whieh the. olds. ar e is red th re p c to ea h. other s hey are j ined a d thev e s o the shell re t immed pr or o b n bee ee- 4,. A proc ss as claimed in claim 1. in ch the molds are registered with respect to each othe s. they ar oi ed and the. ed es. i t she a e trimm d pr o to in he secl and While it is curved.

A process as, claimed in. e em; which the ends. o the, trimmed sh ll. re overlapped, the. s ll is s ppo t d. n a rotatab e cylinder emi s eked with olt n meta as it is r pidly rotated A. oce as. eleimed in el i in which. the ends. o t e tr mmed shell re. o er pped as the sh l is bac ed w h. m ten et G RGE UNGAY- References Cited in the file oi this patent UNITED STATES PATENTS Number Name Date 889,341 Shuman June 2 1908 985,032 Hess Feb. 21, 1911 1,028,330 Cooper June (1, 1912 1,426,549 Corey Aug. 22', 1922 1,433,763 Warn et a1 Oct. 31, 1922 1,720,430 OBrian et al. r Jul; 9, 1.929 2,000,756 Heck May 7, 1935 2,229,457; Kimball Jan. 21 1941 2507347 Myers, Jr. May "I, 1950 FOREIGN PATENTS Number Country Date 8,743 Great Britain of 1840

Claims (1)

1. A PROCESS OF FORMING CYLINDRICALLY CURVED ELECTROTYPES WHICH COMPRISES MOLDING A PLURALITY OF FLEXIBLE ELECTROTYPE MOLDS FORM ONE OR MORE FLAT PRINTING PLATES TO BE DUPLICATED AS CURVED ELECTROTYPES, JOINING SAID MOLDS TOGETHER ALONG ADJACENT EDGES OF SEPARATE PLATES, CYLINDRRICALLY CURVING SAID MOLDS WITH THE DESIGN SURFACE OF THE MOLDS AS THE CONCAVE SURFACE, ELECTRODESPOSIT-

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