US1607438A

US1607438A - Method of correcting printing plates

Info

Publication number: US1607438A
Application number: US28260A
Authority: US
Inventors: Leslie W Claybourn
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-05-05
Filing date: 1925-05-05
Publication date: 1926-11-16
Anticipated expiration: 1943-11-16

Description

Nov. 16 1926. 1,607,438

. L. w. CLAYBOURN METHOD OF CORRECTING PRINTING PLATES Filed May 5. 1925 5 Sheets-Sheet 1 Nov. 16 1926.

L. W. CLAYBOURN METHOD OF CORRECTING PR1 NTING PLATES Filed May 5 Sheets-Sheet 2 Nov. 16 1926.

L. W. CLAYBCURN METHOD OF CORRECTING PRINTING PLATES 5 Sheets-Sheet 5 Filed May 5 1925 Nov. 16 1926.

| w. CLAYBOURN METHOD OF commune PRINTING PLATES Fi y 5. 1925 5 Sheets-Sheet 4 //V VE N TOR Nov. 16 1926.

' L. w- CLAYBOURN METHOD OF CORRECTING PRINTING PLATES Fi y 5, 1925 5 Sheets-Sheet 5 PIIDD'IPI'III) Patented Nov. 16,1926.

PATENT OFFICE.

LESLIE W. CLAYBOURN. OF MILWAUKEE, WISCONSIN.

METHOD OF CORRECTING PRINTING PLATES.

Application filed May 5,

My present invention is an elaboration upon the invention shown, described and claimed in my application for patent on improvements in method of correcting printing plates and printing plates produced thereby. filed in the United States Patent Oifice March 19, 1921, Serial No. 453,665, especially to that portion thereof concerned in compressing the entire printing plate, whether the printing plate be fiat or curved, and reducing the same to uniform thickness between its printing surface and its rear supporting face.

It is the object of my invention to bring all portions of the printing surface into the same surface, that is. into the same plane if the plate be a fiat plate and into the same curved surface of a sector of a cylinder if the plate be a curved plate. by pressure ap plied to elevations in the rear face of the printing plate; further, to compress the body of the printing plate in novel manner for correction of its printing surface with pressure greater than the printing pressure applied tothe printing plate; and, further. to cause the compression of the body of the printing plate by pressure upon protuberances thereof so arranged that relief of pressure displacement may be had in recesses in the body between said protuberances.

I have found that when printing from printing plates as heretofore made, not employing my improvements, the printing surface of the printing plate will let down or the body thereof compress during printing in uneven manner away from the printing surface to cause imperfect printing. It is a further object of my invention. therefore, to compress the body material of the printing plate'in novel manner to a density at least as great as any density which would be imparted to theprinting plate by printing pressures, especially at the solid portions of its printing areas.

I have found in practice, that compression of a printing plate by my improved metho is ordinarily sufiicient to place the printing surface thereof in substantially proper printing condition, and that ordinarily little subsequent correction is required to render the plate properly printable, although such subsequent corrections may be made if desired.

I have exemplified my invention as em- 1925. Serial No. 28260.

within the spirit of my invention, within the scope of the appended claims.

The invention will be further readily understood from the following description and plaims, and from the drawings, in which lat- Fig. 1 represents a plan view of an exemplifying printing plate.

Fig. 2 is a cross-section of the same, taken on the line 22 of Fig. 1.

Fig. 3 represents a cross-section of a portion of the printing plate shown in Fig. 1, taken on the line 33 of Fig. 1, to illustrate the usual relations between the printing surface and the backing surface in their crude state, as in old methods, the. plate being shown enlarged to disclose imperfectionsinherent in such plates. J Fig. 4 is a cros:-sectional view of a print- 111g plate having the same printing surface, taken on the same section line as in Fig. 3, but of increased thickness. the rear of the printing plate being provided with protuberances and depressions. the printing plate being shown subjected to compression.

Fig. 5 is a front elevation of an exemplifying machine, partly broken away, for compressing the printing plate.

Fig. 6 is a diagrammatic representation of an instanced compressing effect upon a printing plate.

Fig. 7 is a plan view of the rear side of one corner of a printing plate. illu trating eremplifving protuberances for a printing plate having a preponderancejof intermedi- V 4 ate states of printing surface.

Fig. 8 is a cross-section of the same, taken on the l ne 8-8 of Fig. 7.

Fig. 9sis a plan view of an exemplified rear side of a printing plate having protuberances for a preponderance of solid printing portrons.

Fig. 10 is a cross-section of the same, taken on the line 10--10 of Fig. 9. v

Fig. 11 is a plan view of a similar rear side of a printing plate having protuberances fora preponderance of light printingsurfaces in the printing plate.

Fig. 12 is a. cross-section of the same, taken on the hue 12-12 of Fig. 11.

curved plate, this system also producing un- Fig. 13 isa plan view of a portion of an exemplifying backing for a printing plate having connected pressing faces.

Fig. 14 is a cross-section of the same, taken on the line I L-14 of Fig. 13.

Fig. 15 is a plan view of a portion of an exemplifying backing of a printing plate having recurrent protuberances and depressions in the form of recurrent ribs and grooves. I

Fig. 16 is a cross-section of the same, taken on the line 1616 of Fig. 15.

Fig. 17 is a cross-section of an exemplifying curved printing plate, provided with recurrent protuberances and depressions, similar to those shown in Fig. 11, but which may be of forms corresponding to the forms of any of the protuberances and depressions illustrated in Figs. 7 to 16 inclusive, or of other desirable form.

Fig. 18 is a vertical sectional view of an exemplified machine for reducing a flat printing plate to uniform thickness between its printing surface and its rear supporting face by shaving.

.Fig. 19 is a vertical axial section of an exemplifying machine for compressing a curved printing plate, taken in the plane of the line 19-19 of Fig. 20, partly broken away.

Fig. 20 is a vertical cross-section of the same, taken in the plane of the line 2020 of Fig. 19.

Fig. 21 is a the same.

Fig. 22 is a vertical section of a detail of the same, taken in the plane of the line 22-22 of Fig. 19, and,

Fig. 23 is a cross-sectional view of an exemplifying machine for reducing a curved printing plate to uniform thickness between its printing surface and its rear supporting face by shaving.

It has heretofore been a usual practice in making ready for the printing from printing plate, to overlay the tympan of the printing press on which the printing perspective view of a detail of plates are to be printed at those portions at which the printing appears too light in the proofs, or to underlay printing plates at such portions, or to both overlay and underlay at the insufficiently printing portions, or to cut away thicknesses in the tympan at unduly heavily printing portions, with the result that uneven surfaces are obtained .both in the tympan and at the bottom of the printing plate, such system making it necessary also to employ a comparatively soft tympan Other systems have attempted to produce the differences between solid and light printing effects by locating the light printing portions of the printing plate lower than the solid portions, if a flat plate or nearer the axis of the plate cylinder, if a evennesses of printing surface. These un-.

even, waving or undulating surfaces at the rear face of the printing plate or at the face of the tympan, or both, also in the course of printing. or during a long run, vary from their original states, especially under the heavy print-pressures necessary to be employed under such old methods, resulting in difierences in appearance of the printing during different portions of the run and making subsequent make-readies necessary.

I avoid all these objections by bringing the printing surface of the printing lines and areas throughout the printing plate in novel manner equidistant from the rear or supporting surface of the printing plate, and bringing these two surfaces respectively within the same surface. I am enabled thereby to bring the backing or supporting surface and the printing lines into coaction with surfaces which are equidistant from each other and located wholly in two spacedapart surfaces, namely, the surface of the plate-bed or plate-cylinder of the printing press and the surface of a coacting comparatively hard tympan sheet.

I am thereby enabled to produce superior printing, and also 'to print with a tympan whose impression surface is throughout sub,- stantially in the same surface, so that successive printings by different plates or printing elements may be received by the same portions of the tympan, whereby my invention is especially adaptable for so-called wet printing, in which successive printings in different colors are printed upon the same sheet during its single passage through the printing press, as well as to all other characters of printing, enhancing the appearance and beauty of the printing and enabling me to reproduce the appearance of solids. highlights and intermediate printing effects, in

highly contrasted relations in the printing from coordinated plates representing different colors, and avoiding the humps and hollows in the make-ready for one color which are detrimental to the make-ready for another color in the old methods mentioned, irnd enhancing true registry of the printing mes.

My invention further enables rintin to be accomplished with considerably lighter printing presses and with harder tympans than under such older methods now in general use and materially increases the numbers of imprints which can be obtained from one make-ready of the printing subject. By my improved, further, the solid portions of the printing plate are compressed to greater 7 of printing effect throughout long periods of The distances and surfaces mentioned are intended to be measured by print-pressures, as they are ordinarily too refined for observation by the naked eye.

The printing plate is exemplified at 51 and, in the present exemplification, comprises a printing shell 52 which may be of usual electro-deposited, metal, for mstance, copper deposited on the matrix in electro-plating, and a backing 53 onvwhich the printing shell is fixedly supported, usually cast into the shell. This backing is usually a composition composed for example of lead, tin. and antimony, in the proportion, for example, of ninety pounds of lead and five pounds each of tin and antlmony. It is obvious however, that other backing material may be employed and that my invention is not limited to printing plates thus formed.

In carrying out my improved method, the printing plate may at its margins be provided with bearers 55, which may if desired be separated from the printing surface by grooves 56, and the printing plate may also have intermediate or interior bearers exemplified at 57. The marginal bearers and intermediate bearers may be so associated as to make it advisable to merge the same, as shown at 58. These bearers are useful for receiving the compressive strains at the edges of the plates, and in intermediate portions of the plate which would otherwise be devoid of support in the plane of the printing surface. These bearers are removed from the plate in the course of op eration on the plate, subsequent to compression by my improved method, the marginal bearers being removed, as by sawing, and the interior bearers being removed, as by routing, the latter operation leaving spaced in the face of the plate free of printing function. My improved method is, however, employable on plates which are not provided with bearers.

I have in Fig. 1 shown an exemplification of the printing face of a printing plate to be corrected, illustrating the differences in solidities of the printing portions of a print? ing plate, and its bearers. In this exem plification the part 61 represents a solid portion, the parts 62 intermediate portions, and the parts 63 high-light or light printing portions of the printing surface.

One of the characters of printing plates upon which my present invention is employable is shown, described and claimed in Letters Patent N 0. 1,318,967, granted on my application, and dated October 14, 1919, for method of curving printing plates and printing plates curved thereby.

In my improved method, the printing plate is either formed of approximate uniform thickness, or reduced thereto, as by approximately straightening the same at its printing surface and shaving the rear face thereof. The approximate straightening of the printing surface may be accomplished by laying the printing plate printing face down on a substantially heavy metal slab having a planeimposing surface and pounding the back of the printing plate through the medium-of a usual imposing block and mallet.

The shaving may be accomplished by any usual means, and I have shown an illustrative machine of this character in Fig. 18, in which 65 represents the bed of the machine, which bed is for instance of metal having a plane surface. A carriage 66 has thereon short knife-sections 67, between which bearing rollers 68 are located to press the printing surface of the printing plate toward the bed. The carriage is suitably driven, as by means of a pinion 71 at each side of the carriage, fixed to a shaft 72,

journaled in a bearing 73 in each side of the frame 74 ofthe machine. The pinions mesh with toothed racks 75 on the respective sides of the' carriage, the carriage being guided in its reciprocations in true lines by suitable guides 7 6 at the respective sides of the frame. Movement of'the carriage over the printing plate, laid printing face down upon the bed, causes shaving of the backing face of the printing plate, for re ducing the printing plate to proximate uniform thickness between its printing surface and its rear face, but preferably thicker than the finished printing plate to allow forthe compression of the plate and for subsequent shavings.

The shaving machine exemplified is more fully shown, described and claimed in Letters Patent No. 1,282,013, granted me October 15, 1918, for method of and apparatus for shaving printing plates, it-being assumed that such shaving machine having a flat bed and linear shaving movement between the shaving elements and the printing plate be employed.

The printing plate in such condition is of approximate uniform density throughout, this density of backing material being exemplified by the uniform spacing of the lines representing the cross-sectioning of surface are not in the same surface. that is,

in the same plane if the printing plate be a flat plate or the same curved surface of thesector of a cylinder. if the printing plate be a curved plate. The printing plate, when first formed, or when reduced to approximate uniform thickness throughout at its printing lines, has as a matter of fact and 1n printing effectundesirable irregularities loo in its printing surface and in thicknesses in different portions of the plate, forming undue high or low places in the printing'surface, resulting in imperfect printing impressions and the practice heretofore of over-laying the tympan or underlaying the plate or the block on which the plate is mounted, or cutting out thicknesses of the tympan.

In my improved method, I compress the body of the printing plate, and solidify any soft or porous spots in the plate, and press all portions of the printing surface of the printing plate toward a given surface in order to locate all portions of the printing surface in the same surface.

The printing plate, especially the backing material or body thereof, is in my improved method therefore compressed preferably selectively according to the solidities of the printing portions of the printing plate. Thus the portions of the printing plate at the printing portions thereof which are solid, are compressed to greater densities than those portions thereof which are provided with light or intermediate solidities of printing surface. These difference in densities are indicated in Fig. 4 by the differences in the closeness of the cross-sectional lines.

In order to more effectively compress the printing plate, I prefer to provide the backing thereof with protuberances and recesses, the protuberances being exemplified in Figs. 4, 5 and 6, as elevations 77 between which there are depressions 78. These elevations preferably have "sloping sides 79, forming the walls of the depressions, the sides sloping away from each other at the respective elevations for contracting the depressions toward their bottoms, the elevations widening toward their bases so as to distribute the compressive action upon the outer ends of said elevations over progressively greater areas to obtain greater uniformity of pressure at the printing face of the printing plate, and to consequently compressively act throughout the area of .the printing plate.

The object of providing protuberances or elevations in the backing of the printing plate is. to obtain greater uniformity of pressure throughout the plate in compressing the same and to obtain greater densities of the backing material than if it' were attempted, for instance, to compress a printing plate having a substantially continuous backing surface between substantially continuous coacting surfaces.

The protuberances and recesses .may, if desired. be formed in the printing plate when the printing plate is formed. It desired, however, the protuberances or elevations and recesses may be formed in the rear face of the body of the printing plate after 7 the printing plate hasbes l made, as by any usual means, for ihst .nce, by employing saws or cutters for cutting the grooves in the backing of the printing plate.

I accomplish the compressing operation preferably by placing the printing plate with its printing-face upon a plane hard surface, preferably'of greater area than the area of the printing plate, as of a resistance member 80, which may be a hardened steel slab, all portions of which surface are in the same surface, and providing a compressing mgnber, exemplified at 81, preferably of greater area than the area of the printing plate, which I apply to the rear face of the printing plate, this compressing member preferably having-a plane surface acting upon the outer ends of the elevations in equidistant relations throughout from the hardened surface of the resistance member. The compression preferably takes place shortly after the printing plate has substantially cooled or set and before the hardening acquired by lapse of time takes place.

Pressure is applied to cause approach between said compressing member and the coacting resistance member, to compress the printing plate between said surfaces, for preferably compressively acting upon the body of the printing'plate which, in practice, is usually softer or more readily com pressible than the material of the printing surface of the printing plate, which is usually a printing shell.

One of the objects of providing the protuberances or elevations in the printing plate is to permit compressive action on the printing plate with a minimum expenditure of compressive power and to provide for a more uniform compression of the printing plate and for a lateral relief of compressive action at the sides of the protuberances or elevations.

Thus, referring to the diagram in Fig. 6, the direction of pressure applied is perpendicular to the printing surface of the printing plate, as indicated by the arrow (1. As the pressure increases to cause compression of the body of the printing plate, the area over which the pressure is exerted is increased, but the pressure is exerted in substantially the same directions, as indicated by the dotted lines I). The area of ressure increases laterally in all directions rom the outer ends 82 of said elevations, for applying compressive pressures to the body of the printing plate under the depressions 78.

emplified by the dotted lines 83.

- This pressure for compressing the body of the printing plate to desired extent, also causes lateral spreading or bulging of the side walls of the elevations into said depressions, as indicated by the dotted lines 84, and the pressure in the body of the prmting plate will also be relieved by an upward The progressive increase in area may be ex-- spreading or bulging of the bottom walls of the depressions, indicated for instance by the dotted line 85. The pressures perpendicular to the surface of the printing plate are further equalized throughout the area of the printing plate, any excess compressive action finding relief in the depressions, and spreading of the printing plate at its printing surface is thereby avoided, so as to ma ntain the printing lines at their original distances from each other, for providing prepared printing plates, the printing lines of which will accurately register with each The compression may be accomplishedby any suitable device capable of imparting substantially great pressures, for instance, a hydraulic press comprising a bed 88, on which the resistance member 80 is received and upon which latter the printing surfaceof the printing plate is laid. The compressing member is placed upon the back of the printing plate, so as to coact with the backing material of the printing plate, or the. outer formations of said backing. A plunger 89 of the press coacts with the bed thereof, its presser surface and the bed surface being equidistant from each other throughout their areas, and the movable element, instanced as the' plunger, being guided as by guides 90, as is usual in a press of this character, in true right lines perpendicular to said surfaces when applying the pressure. The applying of the pressure causes the compression of the printing plate in manner herein described, and solidifies the same, including soft or porous spots or portions therein.

I have in Figs. 5 to 12 inclusive shown the compressing elevations as having square outer areas. Other forms of compressing elevations may be employed, or the compressing elevations may be connected with each other for forming disconnected de-. pressions between said elevations, for instance, 'as shownvin Figs. 13 and 14, in which thecompressing elevations are exemplified by the continuous elevated portions 91 having the depressions 92 therein, the latter having sloping walls 79.

If desired, the elevations'and the depressions therebetween may be continuous across the backing, as instanced by the ridges 93 and the grooves 94 therebetween, in Figs. 15 and 16. The ridges and the grooves may extend along the length or across the width or in other direction at therear of the body of the printing plate.

I further prefer to provide the rear face of the printing plate with compressing elevations of different areas and spacings according to the average solidities of the printing surface of the printing plate to be compressed, and prefer that the greater the amount of solid areas there are in the print- (See Fig. 5.)

ing surface of the printing plate, the greater shall be the proportion of compressing elevations in the backing of the printing plate. Thus, as examples, I have in Figs. 9 and 10 shown respectively a plan view and a cross-section of a portion of a printing plate having desirable formations for a large amount of solids in its printing surface. Such backing may for instance have fortyfive percent of its area as elevation surface and fifty-five percent of its area as depressions. The outer ends 82 of the elevations may, for instance, be five thirty-seconds of an inch square and the sloping sides 7 9 have an inclination of, sixty degrees.

In Figs. 4, 5, 7 and 8, I have exemplified respectively a cross-section and a plan view of a portion of a printing plate provided with formations which I prefer to employ in a printing plate having substantially balanced areas of solids and high-lights or intermediate conditions of solidities of printing surfaces, in which the area of compressing surface may amount to twenty-five percent and the areas of depression in the plane of the rear surface amount to seventy-five per-- cent of the total area of said rear surface. The outer ends 82 of the elevations may be exemplified as one-eighth of an inch square, and the sloping sides 7 9 have an inclination of sixty degrees.

I have in F igs; 11 and 12 illustrated respectively a plan view and across-section of an exemplified portion of a printing plate having formations which I prefer to employ in printing plates having a preponderance ion of high-lights or light printing surfaces, on p ends 82 of the elevations to be three thirtyseconds of an inch square, and the sloping sides 79 as having an inclination of sixty degrees. The said areas are instanced in.- the. printing plate after the printing plate has received said formations and its preliminaryor initial shaving to reduce the printing plate to substantial uniform thickness.

I prefer that such elevations shall be of such heightv and the lateral walls thereof slope to such extent that compressive action directed perpendicular to the printing surface may progressively spread in the body of the printing plate so that said compressive action may be distributed throughout the area of the printing plate at the printing shell or printing surface and be exerted in such manner that a,spreading of the printing plate orof the lateral distances between printing lines is avoided. Exces-.

ing or spreading of said side walls and a relieving of excessive pressure upon the printing plate by the flowing of the backing material under pressure into said depressions. Said elevations may, for instance, have a height of one-twentieth of an inch. and the bases of the sloping sides be spaced apart to provide the approximate areas mentioned. These examples are, however, exemplifications and not limitations, as the areas, proportions of areas and inclinations may vary within the spirit of my invention.

Further instancing desirable pressures to be employed in my improved method, and instancing a printing plate comprising an electro-deposited copper shell and a backing composed of a cast backing metal, such as hereinbefore described, comprising lead, tin and antimony, it may be stated that I have found desirable pressures for instance upon a printing plate having a substantially solid printing surface, and a size of ten inches by twelve inches or one hundred and twenty square inches, to be a range of from two hundred tons to two hundred and fiftytons for the entire plate, equaling a range of from substantially one and two-thirds tons per square inch of printing plate to two and one-twelfth tons per square inch of printing plate; that when compressing such-printing plates of the given size having a medium solidity of printing surface, aggregate pressures having a range of from one hundred tons to two hundred tons pressure may be employed, representing pressures having a range of from five-sixths of a ton per square inch to substantially one and two-thirds tons er square inch; and that when compressing such printing plates of such given size having a preponderance of high-lights or light printing portions, aggregate pressures having a range of from fifty tons to one hundred tons may be employed, representing a range of from substantially fivetwelfths of a ton to fiv-e-sixths of a ton per s uare inch of printing plate; and that w on compressing printing plates of such given sizes inwhich the backing material is very hard, greater pressures may be employed.

The medians of the respective ranges of pressures have been found suitable for the averages of said characters of plates. The pressures mentioned may vary according to the character of backing material and print ing face employed, and are given as instances and not as limitations.

I have found, in printing plates, especially such as comprise printing shells of electrodeposited metal, and also in plates otherwise formed, that the edges or boundaries, as at 96, of printing surfaces are in practice higher or more prominent in unprepared printing plates than the printing surfaces, as at 97, between such edges or boundaries. Exemplifying this condition, I have found that, for instance, the dots in highlight areas, when subjected to highly magnified inspection, are really not dots, but are inclosing circles, the inner areas of which are sunken and either do not print or print Very lightly, although to the naked eye they appear as fully developed dots.

By employment of my improved method. I am enabled to press the printing areas between the boundary edges or lines into substantially the surfaces of such printing boundaries or lines, so as to minimize the difference between such areas and said boundary edge or lines in printing for enhancing the printing eifect.

By means of my invention, I further bring all portions of the printing surface into the same surface so as to minimize the necessity for overlaying and cutting into the tympan and underlaying, and producing highly efficient printing.

A printing plate is in practice, during the printing operation, subjected to greater pressures per area at the solid printing portions thereof than it is at the other portions thereof, for instance, the high-light or light printing portions of the same.

In subjecting the printing plate to the compressive actions hereinbefore described, I produce greater densities in the solid portions of the printing plate than in the highlight or light printing portions of the same.

In the high-light or light printing portions of the printing plate there are greater areas in the printing face which are considerably depressed for avoiding printing thereof, and while all parts of the area of the printing plate are subjected to the same premure in the compressive actionupon the same, the pressures at the solid portions are resisted by greater areas of contact between the printing surface and the coacting resistance plate, upon which the same rests, than at the high-light or light printllO ing portions of the printing plate, where greater unprinting areas are located. These unprinting areas permit a portion of the metal being compressed to find relief in such unprinting areas, for causing less densities in the metal of the backing of ,the plate at those portions of the printing plate having more open areas in their printing surface than the solid portions thereof, this relief of density varying according to the solidities of the-printing portions, the high-light or light printing portions being provided with the; least densities. Y

The relief of density mentioned is received in the unprinting depressions. which are in practice increased in depth where mecessary, as by routing or otherwise, in finishing the plate, but the distance of perpendicular yield of the bottoms of these depressions toward the printing surface is slight.

The compressive action upon the printing plates in my improved method is preferably greater than any compressive action on said printing plates by any pressures to which the printing plates are subjected in the printing operation, to avoid compression of the printing plate during printing.

\Vhen printing from a plate made according to my improved method, those portions of the plate which are subjected to the greatest pressures-per area in the printing operations are resisted by the greater densities in the printing plate, while those portions of the printing plate which are subjected to the less pressures per area in the printing operation, for instance, the high-light or light printing portions of the printing plate, are resisted by the portions of the printing plate of less density, providing resistances in the printing plate proportional to the printing pressures per area required for proper printing of the various printing portions of the printing plate.

I do not herein claim the means for effecting such pressures, having shown, described and claimed the same in a copending application, filled by me in the United States Patent Office December 7, 1922-, as Serial No. 605,455, for patent on improvements in means for compressing printing plates.

The printing plate is thus reduced to uniform thickness between its printing surface and its rear supporting surface, and said surfaces are each in the same given surface.

The printing plate may be subjected to subsequent shavings and provings, and may be corrected by pressing said surface depressions toward the plane of the balance of the printing portions of the printing plate so as to be in the same plane therewith, and subsequent shavings of said backing surface take place, for instance, in manner shown, described and claimed in my aforesaid coopending application Serial No. 453,665, the printing plate .being finally reduced to uniform thickness as determined by printing pressures, with its printing surface and its rear supporting face located respectively in parallel surfaces as determined by printing pressures, and its bearers removed, and its edges provided, if desired, with suitable plate-holding means, all as more fully shown, described and claimed in my aforesaid copending application Serial No. 453,- 665.

If a curved printing plate is to be formed, an example of which is shown, described and claimed in the aforesaid Letters Patent No. 1,318,967, such curving may be accomplished, preferably after the compression of said printing plate as hereinbefore described, or other methods of curving the printing plate may be employed.

When the printing plate has been curved it may be again subjected to compressive acthe flat printing plate, or said initial shaving may be dispensed with, or before or after the back of the printing plate is provided with its protuberances and depressions. These protuberances and depressions may, if de sired, be formed in the printing plate after curving thereof, and, if desired, the compression of the printing plate while fiat may be dispensed with, and the full compression desired imparted to the printing plate in its curved form.

I have in Figs. 19 to 22 inclusive, illustrated an exemplifying machine by means of which compression of curved printing plates may be obtained, the machine and method being further shown, described and claimed in my aforesaid copending applications Serial Nos. 453,665 and 605,455. In this exemplification there is a bed 101 which has a supporting face 102, preferably of greater area than the area of the printing plate and harder than the printing face with which it is to coact, and preferably formed on the sector of a cylinder having the diameter of the path of the printing surface of the printing plate while printing. The curved printing plate, represented at 105, is laid on" this curved surface, with its printing face toward said surface. Pressure is applied for causing the printing surface to intimately approach this curved surface so as to locate the printing surface in the curved surface of the sector of its proper cylinder.

The printing plate is then compressed preferably on linessubstantially perpendicular to the printing surface, or by pressures directed radially of said surface, and preferably in manner to 'maintain the distance relations, in the curved surface of the sector of the printing surface, between the printing lines in said surface, in order to maintain the registry functions of the printing plate.

In order to more effectively compress the curved printing plate, I prefer to provide the backing thereof with protnberances and recesses, shown as elevations 77, between;

which there are depressions 78, these elevations preferably having sloping sides 79, forming the walls of the depressions, the elevations, depressions and sloping walls being formed similarly to the elevations. de-

'pressions' and sloping walls in the backing of the flat plates herembefore described, and

may be of the various forms and contours or in the form of ridges and grooves as hereinbefore described with reference to the flat plates.

I have exemplified compression of the curved printing plate as accomplished by means of a compressing member represented generally at 108, having a compressing face arranged on the curved face of the sector of a cylinder concentric with the sector of the cylinder of the resistance member, the compressing member preferably comprising sectors of a cylinder for coacting with the curved surface of the back of the curved printing plate. The compressing face of the compressing member coacts with the protuberances in the backing face of the printing plate.

I have shown the curved compressing face of the compressing member arranged on compressing plates 110, suitably secured to compressing bodies 111, as by tongue and groove joint 112 between the same, or the compressing plate and its body may be formed as an integral structure. The respective compressing plates and their respective bodies compose sectors of the compressing member 108, which are arranged to be moved radially with relation to the curved printing plate.

The dividing planes between sectors of the compressing member may, if desired, be coincident with the depressions between elevations in the backing of the printing plate, the curved printing plate being preferably placed in the compressing machine in manner to provide this relation.

An exemplification of means for causing the compressing movement may comprise a ram 115, moved in. a guide 116, in a frame 117 of the machine, and having wedge-faces 118 thereon, arranged as sectors of frusto-.

cones, which coact with complemental wedge faces 119 on the sectors of the compressing member. Any suitable means may be provided for operating the ram. I have shown the same as provided with a screw 120, with which a nut 121.is threaded, the nut being shown as in-thehub ofagear 122. The nut is prevented from moving. endwise, but is pe'rmittedto'rotate. The-gear 122 is rotated bysuitable gearing operated by a shaft 124 journaled in bearings 125 of the frame, and having a'hand-wheel 126 thereon for operating the same.

The sectors of the compressing member are provided with radially arranged guides 127, which are guided in guidewavs 128, in aprons 129, 13(7, of the machine frame, the sectors being guided in similar paths at their respective ends. The sectors may at that end thereof toward which the ram moves, be provided with extensions 131 and additional guides 132 slidable in guideways 133.

. The respective sectors are at each end thereof providedv with a lugj 134, a spring 135 between said lug and a ledge 136 or. the apron, normally urging the sector toward its operating part and normally urging separation between the compressing member and the curved plate.

Means may be provided for ready reception'of the plate between the bed and the compressing member, and for removal of the plate from the space between said bed and compressing member, as more fully shown, described and claimed in my aforesaid copending applications Serial Nos. 453,665 and 605,455. The bed is held unyieldingly against stops 137 on the frame during the compressing of the printing plate.

The radial movements of the sectors of the compressing member are substantially perpendicular to the various portions of the printing plate with which said sectors coact.

The action and results of compression and solidification of the curved plate are the same as heretofore explained in connection with the compression and solidification of flat plates. The portions of the curved printing plate comprising solid printing areas are compressed to greater density than the portions-of the plate at which lighter printing surfaces are located and the portions comprising intermediate printing areas are compressed to intermediate densities.

I do not herein claim the invention embraced in the machine herein shown and described for effecting compression of the curved printing plate, having shown, described and claimed said invention in the copending application Serial No. 605,455, aforesaid.

It is obvious of course, that other means i may be employed for causing approach and recession between the curved printing plate and a compression member, or for causing compression of the curved printing plate, within the spirit of my invention and the scope of the appended claims.

- The shaving of the inner face of the curved printing plate may be accomplished by laying the curved plate in a suitable machine in a trough 140, (see Fig. 23), with the printing face of the curved printing plate presented to the wall of the trough, and with one edge of the plate against the longitudinally extendingstop 141, and by passing a rotary facing cutter 142 which extends lengthwise of and parallel with its axis of rotation and with the axis of the plate, across the innerface of the curved printing plate.

The pressures employed in compressing curved printing plates may be similar to the pressures hereinbefore described with refererice to flat printing plates, and conform to the pressures per area and according to solidities of the printing plate, and the protuberances in the body of the printing plates may be similar to the protuberances -hereinlit - or, if desired, the diameters and shapes of the printing plates may be changed after correction thereof, within the scope of the appended claims.

The successive shavings of the backing of the printing plate whether the plate be flat or curved, successively reduce the heights of the protrusions or extensions and the depth of the recesses or grooves. These extensions may if desired be entirely removed when finishing the thickness of the printing late.

p My improved method enables a printing plate to be obtained having a printing surface, the printing lines of which are located in the same surface, that is. the same plane if it be a straight plate or the same curved surface of the sector of a cylinder if the plate be a curved plate, as determined by print pressures, with the printing lines in the printing surface and the rear supporting surface equidistant from each other. The tympan surface upon which the sheets of paper or other material being printed are laid in the printing operation, is also in a given surface, either plane or cylindrical, and is comparatively hard, so that the printing contact is what may be termed a kiss contact between the paper and ink for transferring the pigments of ink to the paper, and avoiding all rubbing contact between the paper and the ink which is incident to causing the paper to be received in depressions or causing the paper to be bent over bulges in the faces of make-readies as now generally employed.

Having thus fully described my invention, what I claim as new, and desire secure by Letters Patent, is:

1. The method of correcting a printing plate which comprises providing said printing plate with elevations and depressions substantially as described at its back, applying suflicient pressure to said printing plate between opposed faces in directions substantially perpendicular to the printing surface of said printing plate to cause compression vof the body material of said printing plate and spreading of said elevations into saiddepressions.

2. The method of correcting a printing plate which comprises providing said printing plate with elevations and depressions substantially as described at its back, ap-

plying sufficient pressure to said printing plate between opposed faces in. directions substantially perpendicular to the printing surface of said printing plate. to cause compression of the body material of said printing plate and spreading of said elevations into said depressions, and reducing said compressed printing plate to uniform thickness gauged by printing pressure between its printing portions and its rear supporting face throughout its print-ing portions.

3. The method of correcting a printing plate which comprises providing the rear face of said printing plate with recurrent elevations and depressions substantially as described, compressing said printing plate throughout its printing areas by pressures between opposed surfaces all portions of which are respectively in the same surface and in directions substantially perpendicular to said printing areas and causing relief of flow of the material of the body of said printing plate at said compressed por tions from said elevations into said depressions, and maintenance of' lateral relations between the printing lines in the printing surface of said printing plate.

4. The method of correcting a printing plate which comprises providing the rear face of said printing plate with recurrent elevations and depressions substantially as described, compressing said printing plate throughout its printing areas by pressures between opposed surfaces all portions of which are respectively in the same surface and in directions substantially perpendicular to said printing areas and causing relief of flow of the material of the body of said printing plate at said compressed portions from said elevations into said depressions, and maintenance of lateral relations between the printing lines in the printing surface of said printing plate, and reducing said printing plate to equal thickness as predetermined by printing pressures between its printing portions and its rear supporting face throughout its printing areas.

5. The method of correcting a printing plate which comprises providing the rear face of said printing plate with recurrent elevations and depressions substantially as described, supporting the printing surface of said printing plate on a surface all portions of which are in the same given surface and while so supported compressing said printing platethrougho'ut its printing areas by pressures in directions substantially perpendicular to said printing areas and causing relief of flow of the material of the body of said printing plate at said compressed portions from said elevations into material of said rinting plate and causing bulging of said s oping walls laterall into said depressions and maintenance of ateral relations between the printing lines in the printing surface of said printing plate, and reducing said printing plate to equal thickness between its printing'portions and its rear supporting face throughout its printing portions.

7. The method of correcting a curved printing plate provided with an outer printing surface, which comprises providing the back of said printing plate with elevations and depressions substantially as described, applying sufficient pressure to said curved printing plate between opposed faces in aplurality of directions respectively substantially perpendicular to the printing surface of said curved printin plate and causin compression of the body material of sai curved printing plate and spreading of said elevations into said depressions, and maintenance of lateral relations between the printing lines in the printing surface of said prlnting plate,

8. The method of correcting a curved printing plate provided with an outer print- 1ng surface, which comprises providing the back of said printing plate with elevations and depressions substantially as described, applying sufficient pressure to said curved printing plate between opposed faces in radial directions substantially perpendicular to the printing surface of said curved printing plate andcausin compression of the body material of said printing plate and spreading of sald elevations into said depressions, and maintenance of lateral relations between the printing lines in the printing surface of. said printing plate.

9. The method of correcting a curved printing plate having an outer printing surface and a body which comprises providing the rear face of said body with elevations and. depressions substantially as described, supportin said outer printing surface on a curved face which is the sector of a cylinder, applying a curved face which is the sector of a cyhnder to the inner face of said curved printing plate, said curved sectors beingsubstantially concentric, and causing approach between said curved faces to compress said printing plate and spread the walls of said elevations laterally into said depressions, and maintenance of lateral relations between the printing lines in the printing surface of said curved printing plate.

10. The method of correcting a curved printing plate having a curved outer printing surface, which comprises providing the rear face of the body material of said printing plate with elevations and depressions substantially as described, supporting said curved outer printing surface by a curved face which is the sector of a cylinder and applying pressures upon' said inner surface of said curved printing plate in directions substantially radial with relation to said curved supporting face and causing compression of said elevations and maintenance of lateral relations between the printing lines in the printing surface of said printing plate.

11. The method of correcting a curved printing plate having a curved outer printing surface which comprises providing the body material of said printing plate with elevations and depressions therein substantially as described, supporting said curved outer printing surface b which is the sector of a cy inder and applying pressures upon said inner surface of said curved printing plate in directions substantially radial With relation to said curved sup orting face and causing compression of sai relations between the printing lines in the elevations and maintenance of laterala curved face i printing surface of said printlng plate, and

whereof, I have hereunto signed my name.

LESLIE w. oLAYBoURiv.