US3426679A

US3426679A - Multi-color printing in a single impression

Info

Publication number: US3426679A
Application number: US585919A
Authority: US
Inventors: Thomas B Rhines
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1966-10-11
Filing date: 1966-10-11
Publication date: 1969-02-11
Anticipated expiration: 1986-02-11
Also published as: BE704906A; NL6713709A; FR1548474A

Description

T. B. RHINES M'JL'IL-QOLQR PRINTING IN A SINGLE IMPRESSION Feb. 11, 1969 Sheet of 4 7 Filed Oct. 11, 1966 /\VE\1UR THOMAS B. RHINES M/gf ATTORN EY Feb. 1969 T. s. RHINES MULTI-COLOR PRINTING IN A SINGLE IMPRESSION Sheet 2 of4 Filed Oct. 11, 1966 1% 006a 9 9066a 9 @06 Q @0@ Q T. B. RHINES Feb. 11, 1969 Filed Oct. ll, 1966 Sheet Feb. 11, 1969 T. B. RHINES 3,426,679

MULTI-COLOR PRINTING IN A SINGLE IMPRESSION Filed om. 11, 1966 Sheet 4 of 4 fie, 9

United States Patent 3,426,679 MULTI-COLOR PRINTING IN A SINGLE IMPRESSION Thomas B. Rhines, Glastonbury, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Oct. 11, 1966, Ser. No. 585,919 U.S. Cl. 101-175 11 Claims Int. Cl. B41f 5/18, 31/14 ABSTRACT OF THE DISCLOSURE Apparatus for printing full color reproductions in a single impression in a rotary printing press is described. A single printing plate is provided having a plurality of discrete projections provided thereon in the desired pattern of intelligence, the projections being provided in the basic plate in unit cells which are repetitive in an overall array. Ink transfer rollers lay down a complete ink pattern in three or more colors on a blanket cylinder in a pattern corresponding to the basic repetitive unit cell pattern provided on the printing plate and the printing plate projections are, accordingly,each inked with a single color which corresponds to their location in the unit cell, particular shades and color intensities as well as the requisite pattern being reproduced as a function of the intelligence provided on the printing plate.

This invention relates in general to the art of color printing and, more particularly, to those printing processes wherein multi-color reproductions are effected in a single impression in high speed presses.

Despite extensive developmental efforts in the field, the printing of full color reproductions on high speed presses, such as those used by the large daily newspapers, remains a tedious, expensive and relatively inexact process. Such reproductions are still usually made through the use of multiple impressions of single colors in successive passes of the paper or other material to be printed past the individual single-color printing plates. Separate plates are prepared, one for each color to be applied, and successive separate impressions are made on the paper with each plate, one color imprint being superimposed over the other with appropriate registration to provide the full color illusion in the finished product.

In order to achieve high quality reproduction in this manner, extreme care is necessary in the preparation of the plates to assure proper registration of the various colors, as well as with the alignment of the plates and with the sequencing operations in the presses. Achieving good initial registration of the various color patterns, at very high press speeds and under the usual adverse environmental and schedule conditions prevailing, is usually a substantial task in itself. Even though advances in the field permit a fairly precise alignment of the color patterns, to within 0.001 inch in some cases, the requisite registration is so sensitive that changes occurring during the press run, such as shrinkage or expansion of the paper due to changes in humidity, for example, readily lead to discernible changes in registration, even though the initial alignment was accurate.

Furthermore, the necessity for the close control of ink viscosities and drying rates imposes additional limitations on the system, particularly where one primary color is to be overlaid over another in the printing sequence. In some processes, two or more primary colors are blended to achieve a desired intermediate hue, the initially deposited ink being physically mixed or blended with that subsequently overlaid thereon. In this type process, the first ink must remain sufiiciently fluid to admix freely with the ink of the second color when the second impression is made.

In other inking processes, an optical blending technique is used, the second color being laid over the first only after the first deposited ink has dried. In some cases, the second color partially bleeds into the first with a resultant nonuniformity of print rather than the crisp color pattern intended. In any event, the press speeds and sequencing must be coordinated with the ink compositions, compatabilities and drying rates in order to attain satisfactory results.

The use of full color techniques compatible with the usual black and white printing processes, or run-of-thepaper color, would, of course, be a tremendous boon to the large daily newspapers which generally find it necessary to compete with the other advertising media pri marily on their black and white capabilities. What is obviously still needed in the industry is a color printing system which will produce clear and faithful full color reproductions by means and at speeds compatible with the normal newspaper press runs, and which is economically justifiable in view of the nature of the newspaper business.

It is a primary object of the present invention to provide apparatus and methods for single impression multicolored printing in perfect registration in high speed presses.

A further object is to provide means effecting full color registration in a simple and economical manner.

A still further object is to provide means for reducing the cost of printing plate preparation, the production of a single printing plate for each new picture in color replacing the usual multiple plates currently utilized in these processes.

Still another object is the provision of a printing system wherein full color reproductions may be produced in a single impression in an offset printing press.

An additional feature is the provision of a printing system wherein the intelligence provided on the printing plate comprises interadjacent projections arranged in triangular array for high color saturation of the paper.

A still additional feature is to provide a color printing system wherein no mixing of ink or overlay of one color impression upon another is required to achieve optical blending to provide the intermediate hues.

These and other objects and advantages of the present invention will be described in the detailed description which follows or will be evident therefrom or from practice of the invention.

When referring to the present printing system in detail, it will be convenient from time to time to make reference to the attached drawings of which:

FIG. 1 is a somewhat schematic end view of a preferred inking and printing arrangement usable in connection with the present invention.

FIG. 2 is a fragmentary top view of the system shown in FIG. 1, the view being shown somewhat schematically for the sake of clarity, the size and spacing of the projections on the various ink transfer rollers being illustrated in enlargement.

FIG. 3 is a fragmentary view of a typical projection array as provided on the printing plate, illustrating particularly the preferred triangular arrangement and interlacing of projections. In this view as in the subsequent figures, the view is enlarged.

FIGS. 4, 5 and 6 are illustrations of the respective preferred projection patterns provided on the yellow, red and blue ink transfer rollers.

FIG. 7 is a view of the complete ink pattern laid down by the ink transfer rollers 0n the blanket cylinder.

FIG. 8 sets forth the finished impression made by a single projection on somewhat absorptive paper such as newsprint.

FIGS. 9, and 11 illustrate the degree of color saturation attainable with the close-packed, interlaced triangular array (FIG. 9); the more widely-spaced triangular pattern (FIG. 10); and the close-packed square array (FIG. 11).

It is readily observable that the principal problem in run of-the-paper color stems from the necessity of employing separate printing plates for each color to be applied, since both the material and labor costs and the problem of precise registration of the individual impressions are related to the use of multiple plates. What is really needed is a printing system which utilizes a single plate for color application wherein only one impression is required to lay down the full color pattern. While the advantages of full color printing in a single impression have been previously recognized, as indicated by the patents to Miller, 3,213,787; Marinier et al., 680,533; Japanese patent, 8139/61; and Austrian patent, 51,285; no such system apparently enjoys much utility in the current printing art.

There are several quite obvious problems attendant to the use of a single plate which is adapted to print several colors simultaneously and the difficulties stem, in substance, from one basic problem, i.e., that of applying the proper color ink to each of the appropriate minute projections on the printing plate and no other projections. Of course, in order to correctly accomplish the requisite inking, precise dimensional alignment of the inking system with the printing plate is necessary. This has severely restricted the size of the individual projections and the possible array patterns which can be employed on the printing plate.

A color printing plate with a plurality of large area projections in widely-spaced array may, quite naturally, be more readily inked than a corresponding plate with much finer projections in close-packed array. On the other hand, for good pattern resolution and high color saturation, the dot pattern is preferably held as small as possible, the developed surface area of each projection preferably encompassing an area of approximately 19 x 10 square inches with a separation between projections of perhaps 0.005 inch. With projections of this size, the problem of applying the correct color ink to the correct surfaces and to no others is manifest.

For maximum color saturation, the intelligence provided on the printing plate preferably comprises a plurality of minute projections oriented in close-packed triangular array, an equilateral triangular array having the projections interlaced in a direction parallel to the principal axis of the individual unit triangles being preferred. The triangular array is capable of giving a higher degree of color saturation than the more conventional square array, as best illustrated in FIGS. 9, 10 and 11.

FIG. 9 shows a unit triangle 2 of

projections

4, 6, 8 in close-packed triangular array, the individual projections being so spaced as to preclude any overlap of the ink from the dots due to ink spread 10, as defined by the dashed lines. This spread as indicated in FIG. 8 will be greater or lesser depending upon the ink composition utilized in the process, but, more importantly, upon the absorptivity of the paper. The relationship between the various arrays, and particularly the projection spacing, is shown in the various drawings, r equalling the radius of the projection, r' indicating the radius of the impression including ink spread. With the so-called slick papers common to the magazine field the ink spread will be correspondingly less than that expected with common newsprint. In a sense, however, the ink spread is of some value in the present invention since it permits a somewhat greater spacing between adjacent projections than would be the case with the less absorptive papers. The amount of ink spread can vary from close to zero in the case of slick paper to about 40 percent in the case of newsprint and newspaper ink.

The triangular array of FIG. 9 can yield a maximum saturation of 90.7 percent, this value being from two (for slick papers) to four (for newsprint) times as much as the saturation in the loosely-packed array of FIG. 10. The square array of FIG. 11 is capable of yielding a maximum of only 59.8 percent. The close-packed triangular array yields a significant advantage in color printing, wherein the degree of color saturation which is achievable heavily influences the fidelity of the color reproduction which can be attained.

It will be noted that in the unit cell 12 of the square array of FIG. 11 there appears to be a dot missing at the lower right-hand corner. This stems from the fact that only three colors are illustrated. In todays printing art, this site 14 is sometimes filled with a fourth color, although the fourth color is not necessary to achieve all of the color hues required in the final reproduction, providing the three colors are properly selected. While in the drawings and in the specification, reference is made to red (R), yellow (Y) and blue (B) for the sake of simplicity, according to fundamental physics, the proper colors would normally be magenta, yellow and cyan. Some mixture of the three basic colors may be used as the fourth color.

Although a combination of the three basic colors may be used, the usual practice is to occupy the unoccupied site 14 with black ink to reduce the amount of white background showing through the color thereby deceiving the eye of the viewer and leading to the belief that there is greater color saturation than actually exists. This technique is particularly effective when black ink is used in this location. The pseudo-saturation thus achieved would then amount to about 78.5 percent, which is still considerably less than that achieved with the triangular array of FIG. 9 and is accomplished, generally, only with the addition of a fourth color. In any event, the fact that this stratagem is used to gain less than a 20 percent addition in saturation is evidence in itself of its fundamental importance.

In the context used herein, the term color saturation will be seen to have reference to the percentage of the paper which is covered by colored ink. The smaller this percentage the greater the background white of the paper shows through. As observed by the viewer, the background serves to dilute the colors which are perceived, the reds appearing pink, etc. While dilution of the deposited colors by optical blending with the background of the paper is the method used in the instant case to achieve the pastel colors and other shading in the finished reproduction, it is used effectively only in combination with areas of high saturation and color brilliance. And the requisite brilliance cannot be attained using arrays wherein the background is prominent. In the present invention the area density of the projections is selectively varied on the printing plate to provide the different and sometimes subtle degrees of shading required to produce flesh tones, for example, while retaining high brilliance and color saturation in other areas as desired.

In each unit triangle on the printing plate, the projections occupying the individual apex positions are each inked with a different color, such as red, yellow and blue, as seen in FIG. 3, for example. To adapt the printing plate for color, some or all of the projections are removed from selected areas of the pattern, as indicated at 16 in FIG. 3. Since the ink is transferred to the individual projections in such a manner that a specific projection receives ink of a single color, elimination of the surrounding surfaces which normally carry a different color will result in the printing of only one color in that area of the paper. And as previously indicated, by varying the projection area density in that portion of the pattern, the color may be shaded as desired into the pastels.

In a somewhat similar manner, by the selective elimination of one or more of the projections carrying a given color, various intermediate hues may be provided from the three basic colors. Assuming that red, yellow and blue inks are applied to the projection surfaces forming the apexes of each unit triangle, elimination of the red projection, while retaining both the yellow and blue, as in FIG. 3, will provide to the viewer an overall physiological impression of green in the finished print, darker or lighter shades of green being effected by employing more or less blue and, correspondingly, less or more yellow in a given area. And if the surface area of the individual dots is small enough, the human eye will not discern the individual blue and yellow impressions but only the overall green effect. The overall optical blending effect, moreover, is accomplished with no physical mixing of the various inks or overlay of an ink of one color upon another. The intelligence provided on the single printing plate will, accordingly, not only provide the desired picture pattern but, also, the appropriate precise coloring thereof.

Any convenient method, such as photo-etching, may be utilized in the fabrication of the printing plate, the more conventional black and white plates similar to those used in half tone printing being further provided with the requisite color intelligence as hereinbefore discussed. Although in the instant case, the ink-carrying surfaces of the projections have been illustrated and described as dots, for the purposes of this invention other surface configurations, such as squares, triangles, parallelograms, etc., are contemplated.

The spacing 18 between the individual projections, although preferably uniform on each printing plate, will nevertheless vary from plate to plate as a function of the ink-paper combination. Accordingly, the spacing utilized for the slick papers will normally be less than that suitable for the more absorptive materials. However, once the spacing has been correctly established for the given ink-paper combination in question, it will be substantially invariant in that operation thereafter. The optimum spacing between projections will be such that the ink from one projection, including the spread thereof, will just abut that of the adjacent projections, thereby minimizing effect of the white background and, hence, maximizing the color saturation of the paper.

The general arrangement of a typical printing system adapted to be used in connection with the instant invention is shown somewhat schematically in FIG. 1. The system, as shown, comprises a printing plate cylinder 20, and an impression cylinder 22 in juxtaposition on opposite sides of the paper web 24. The printing plate cylinder may carry one or more printing plates (not shown in this figure) in the usual manner, each plate representing a page or impression to be printed on the paper or other material. As hereinbefore indicated, the printing plates will be provided with the intelligence to be printed including, if desired, the intelligence required for the simultaneous printing of a plurality of colors in the pattern, shade and form called for in the finished reproduction. Since in this apparatus the printing plates are to be mounted upon a cylindrical roll 20, the printing plates will normally conform in curvature and contour to that of the printing plate cylinder and be so attached as to rotate concentrically therewith. Furthermore, the respective projections on the printing plates Will preferably be identical as to configuration and height to simplify the plate fabrication and the subsequent press alignment problems.

A blanket cylinder 26, which effects inking of the printing plate projections in a single pass thereby, is interposed between the printing plate cylinder and the several sets of ink transfer rollers, 28, 30' and 32, with cooperating inking rolls, 34, 36 and 38, respectively. The surface of the blanket cylinder is formed of or covered with a material, such as hard rubber, which is capable of receiving ink from the ink transfer rollers and transferring it in turn to the printing plate or plates in the manner of conventional offset printing. For full color reproductions, three ink transfer rollers are used in the preferred embodiment of the invention. All of the primary colors and the intermediate lines and shades may be provided from these three basic colors which are referred to herein and shown in the drawings as red (R), yellow (Y), and blue (B), although, as previously discussed, other colors may be advantageously employed to yield the optimum results.

As indicated most clearly in FIGS. 2, 4, 5 and 6, each of the ink transfer rollers, 28, 30 and 32, is provided with a plurality of projections on its outer surface, the projections on the respective rollers being sized and. spaced, when the rollers are properly aligned in the printing press, to lay down an ink pattern on the blanket cylinder which conforms to that provided on the printing plate in terms of the overall pattern. Since the projections on the printing plate are established in an overall triangular array, the cooperative effect of the projections on the various ink transfer rollers will be such that a corresponding triangular ink pattern is deposited on the blanket cylinder.

The projections on the printing plate are preferably arranged whereby the red, yellow and blue dots occupy the three apex positions in each unit triangle, as illustrated in FIG. 3. Each of the projections occupying the corresponding position in each unit triangle is accordingly provided with ink of the same color. As shown, and in the most preferred arrangement, the projections occupying the corresponding apex position in each of the unit triangles furthermore lie in spaced parallel rows, 40, 42, etc., and the projections occupying the other apex positions in the unit triangles may be seen to interlace in a direction parallel to those rows, this direction being defined as the principal axis 44 of the unit triangles 2. It will be noted in the embodiments illustrated in the drawings that this axis extends vertically of the paper or, in other words, circumferentially of the printing plate cylinder. This is a preferred orientation as hereinafter discussed in greater detail, but it will be obvious that other orientations are feasible in the practice of the present invention.

With the printing plate projections oriented in spaced parallel rows as hereinbefore described, the similar projections on the ink transfer cylinders are correspondingly arranged in spaced parallel rows in a more preferred embodiment, as best illustrated in FIG. 2. Each of the projections 40, provided on the first ink transfer roller 28, when the roller is properly aligned in the printing press, will deposit ink on the blanket cylinder at a point corresponding to one apex position in each unit triangle of the overall array. The projections 42 on the second roller 30 will deposit ink of a second color at a point corresponding to a second apex position in each unit triangle. And the projections 44 on the third ink transfer roller 32 will, accordingly, deposit a third color ink on the blanket cylinder in the remaining apex position of the individual unit triangles.

In a preferred arrangement, therefore, the projections on the respective ink transfer rollers lie in axially-spaced circumferential rows, and are positioned axially so that the rows of projections on the red ink roller are in alignment with the rows of red projections on the printing plate; the rows of projections on the blue ink roller are in alignment with the rows of blue projections on the printing plate, etc. When three colors are used in this apparatus, therefore, the rows of projections on each individual ink transfer roller will be spaced apart by a distance 46 corresponding to three times the spacing between adjacent rows of projections on the printing plate. Furthermore, the respective rollers will be axially aligned with the printing plate such that the circumferential rows of projections thereon are axially displaced from the rows on each other roller by a distance 48 corresponding to the unit spacing 50 between adjacent rows of projections on the printing plate.

Quite obviously, in addition to the axial alignment discussed above, each of the rollers and cylinders in the press must be rotationally aligned to insure that the ink deposited by the ink transfer rollers on the blanket cylinder are properly, albeit selectively, picked from the blanket cylinder by the projections on the printing plate. Furthermore, the diameters of the various rotating elements, exclusive of the inking rolls, must be such that, during a given press run, the projections on the respective ink transfer rollers always strike a spot on the blanket cylinder carrying the same color. And, in similar manner, the projections provided on the printing plate must, in successive rotations, always contact the blanket cylinder at a spot carrying the desired color. Normally, therefore, the respective cylinders will be formed to be some whole multiple of one another, with respect to their diameters, for simplicity in maintaining the desired repetitive pattern.

It will be noted that, as shown in FIG. 7, the full pattern of ink is always laid down on the blanket cylinder regardless of the characteristics desired in the final reproduction whereas, quite obviously, something other than the complete ink pattern is usually transferred to the paper to provide the desired print. It is, of course, through the intelligence provided on the printing plate, as illustrated in FIG. 3, that the appropriate selection or rejection of ink from the blanket cylinder is effected. In this regard, mention has previously been made of the necessity for aligning the various cylinders both axially and rotationally in order to provide the precise inking desired. However, the requisite alignment between the ink transfer rollers and the blanket cylinder need not be remade solely because the printing plate is changed and, in theory, need never be adjusted, although in practical terms a periodic alignment adjustment will usually be necessary to compensate for wear, etc. In any event, the usual delicate registration problems are substantially minimized as compared to many of the other full color printing techniques.

In addition to the high color saturation attainable with the close-packed, interlaced triangular array, another significant advantage is worth of mention at this point. It is, of course, desirable to maintain the developed area of each of the unit impressions on the paper of such small magnitude that the individual dots are not discernible to the naked eye. However, even when this is done in many of the current multi-color printing systems and, for that matter in many instances of conventional half-tone printing, the overall effect on the viewer is less than satisfactory. While the eye is unable to segregate each individual dot as printed, it is, nevertheless, frequently able to discern a distinct linear pattern made up of microscopic impressions laid without interruption in distinct rows. And this is particularly true in those instances where the orientation of the rows coincides with the normal direction of eye scan for the viewer. For this reason, it is a quite common practice to orient the various rows at some angle to the normal vertical and horizontal direction of eye scan. In the instant invention incorporating the preferred triangular array, while the various projections are arranged in distinct rows, the effect of lineation is, to a substantial degree, markedly reduced in most instances and completely eliminated in others, particularly in those areas wherein a plurality of colors are printed. When the complete ink pattern is laid down on the paper, there is not only no color lineation vertically and horizontally, but none in any direction.

As previously mentioned, the more preferred orientation of the printing plate projections and, correspondingly, the rows of projections on the ink transfer rollers, is circumferential as shown in the drawings. While not essential, this orientation is preferred because it simplifies the alignment of the various rotating members. Another preferred arrangement (not shown) would be to have the projection rows oriented axially of the respective cylinders. And, of course, a combination of the two preferred orientations may be used.

The other possible orientations wherein the projection rows extend neither axially nor circumferentially of the cylinders but at some angle thereto, while workable in the context of the instant invention, are less preferred techniques since the initial registration problems in the press room are increased.

In most of the preceding discussion, reference has been made to the use of three colors, to the use of an interlaced triangular pattern for the various projections, and to a regular sequence of red, yellow and blue dots in an invariant orientation. The apparatus taught herein is readily adaptable to the use of a greater or lesser number of collars in accordance with the requirements in a given operation. Further, while the interlaced triangular pattern is very much preferred, the instant system is usable with other projection arrangements, and the sequencing of colors need not be held invariant. The instant apparatus is very versatile in this regard.

It will be noted, however, in any of the systems described there is perfect registration of the separate color patterns in the finished print, this perfect registration being inherent in the printing plate itself and, accordingly, any stretching, shrinkage or weaving of the paper during the press run may be expected to exert no influence on the registration of the colors. Colors properly applied to the printing plate are faithfully reproduced on the paper regardless of changes in press room environment. Furthermore, costs, as compared to the color printing systems currently enjoying utility, are much reduced since the preparation of only a single printing plate is necessary for each new picture. And the system described is compatible with the equipment and facilities currently available in the usual printing plant.

While the present invention has been described in connection with particular preferred embodiments and arrangements of parts, various modifications, additions and alternative arrangements will be evident to those skilled in the art within the true spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. Apparatus for printing full color reproductions in a single impression in a rotary printing press, comprising:

a rotatable printing plate cylinder;

a conforming printing plate aflixed to the plate cylinder and having the intelligence to be printed provided thereon in relief, the intelligence comprising a plurality of discrete projections arranged in unit cells which are repetitive in an overall array, the respective projections each having a discrete surface area for receiving ink;

a plurality of ink transfer rollers aligned with the printing plate and having a plurality of discrete projections thereon, the projections on the first of the rollers occupying a position coincident with a first location in each unit cell of an overall array corresponding to that on the printing plate, the projections on a second roller occupying a second location in each unit cell, the projections on a third roller occupying a third location in each unit cell, the rollers acting in concert to provide a complete ink pattern in each unit cell;

a blanket cylinder interposed between and in contact with the plate cylinder and the ink transfer rollers, the blanket cylinder being rotatable in coordination with both the plate cylinder and each of the ink transfer rollers, a complete ink pattern being deposited by the rollers on the blanket cylinder, ink for the intelligence to be printed being selectively picked from the blanket cylinder by the printing plate; and

means for inking the projection surfaces on each of the respective ink transfer rollers with a desired color.

2. Apparatus for printing color reproductions of high resolution, color fidelity and color saturation in a single impression in a rotary printing press, comprising:

a rotatable printing plate cylinder;

a conforming printing plate afiixed to the plate cylinder and having the intelligence to be printed provided thereon in relief, the intelligence comprising a plurality of interadjacent discrete projections in an overall triangular array, the respective projections each having a discrete surface area for receiving ink;

a plurality of rotatable ink transfer rollers aligned with the plate cylinder and having a plurality of discrete projections thereon arranged in an overall array corresponding to that provided on the printing plate, each of the projections on the first of the rollers occupying a position corresponding to one apex position in each unit triangle of the overall array, each of the projections on a second roller occupying a position corresponding to another apex position in each unit triangle, each of the projections on a third roller occupying the remaining apex position in each unit triangle;

a blanket cylinder interposed between and in contact with the printing plate and the respective ink transfer rollers, the blanket cylinder being rotatable in coordination with both the plate cylinder and the individual rollers, a complete ink pattern in triangular array being deposited by the rollers on the blanket cylinder, ink for the intelligence to be printed being selectively picked from the blanket cylinder by the printing plate; and

means for inking the projection surfaces on each of the ink transfer rollers with a desired color.

3. Apparatus as set forth, in claim 2 wherein:

the respective projections on the printing plate are substantially identical as to the configuration and height; and

the respective projections on each ink transfer roller are substantially identical as to the configuration and height.

4. Apparatus as set forth in claim 3 wherein:

the projections provided on each ink transfer roller all occupy the same apex position in each unit triangle of the overall array.

5. Apparatus as set forth in claim 4 wherein:

angles of the overall array lie in spaced parallel rows.

6. Apparatus as set forth in claim 5 wherein:

the rows of projections of the respective ink transfer rollers extend circumferentially thereof.

7. Apparatus as set forth in claim 3 wherein:

three ink transfer rollers are provided, the first roller being inked with a first color, the second roller being inked with a second color, and the third roller being inked with a third color.

8. Apparatus as set forth in claim 7 wherein:

the first, second, and third colors are selected to provide the entire color spectrum desired in the finished reproduction.

9. Apparatus as set forth in claim 7 wherein:

the first, second, and third colors are cyan, magenta,

and yellow, respectively.

10. Apparatus as set forth in claim 3 wherein:

the spacing between adjacent projections on the printing plate is selected so that the ink pattern deposited by one projection just abuts that deposited by an adjacent projection.

11. Apparatus as set forth in claim 10 wherein:

the developed printing surface area of the individual projections is about 1-9 x 10 square inches.

References Cited UNITED STATES PATENTS 833,908 10/1906 Ames 101-175 851,039 4/1907 Southgate 101175 2,275,062 3/1942 Lathey 101211 XR 2,733,656 2/1956 Gottsching 101-175 FOREIGN PATENTS 652,579 11/1937 Germany.

8,17-6 4/1900 Norway.

ROBERT E. PULFREY, Primary Examiner.

the projections on both the printing plate and the J. R. FISHER, Assistant Examiner.

respective ink transfer rollers which occupy the corresponding apex positions in each of unit tri- U.S. Cl. X.R.