US2506427A - Method of preparing gravure printing surfaces - Google Patents

Description

May 2, 195o R. MaCKAY 2,506,427

METHOD ,QF PREPARING GRAVURE'PRINTING SURFACES Filed'NOv. 16, 1946 v2 sheets-sheet 2 HMI.

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ATTORNEY Patented May 2, 1950 METHOD OF PREPARING GRAVURE PRINTING SURFACES Robert MacKay, Louisville, Ky., assigner to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Application November 16, 1946, Serial No. '710,373

2 Claims. (Cl. 101-33) The present invention relates to gravure printing, in which intaglio printing cylinders are employed, and the invention relates particularly to the provision of printing members, particularly copper or other cylinders having etched surfaces with cells or depressions which are variable in depth, so as to provide superior tone effects and detail in the printed image. The primary object of the invention is to provide a method whereby the problem of mis-register in multi-color printing is eliminated in the employment of gelatine as the resist for etching with variable depths in copper or similar printing surfaces. My method eliminates the necessity for making a composite of the images on a positive form which is the practice now followed.

The method commonly used throughout the gravure printing industry to transfer a multicolor picture image to copper and etch this image to form a printing surface consists of the following steps:

(a) From the original .art work a continuous tone negative is made. This negative is reversed into a positive image, or a series of positive images in the case of duplicate units. This positive image is either continuous tone or screen image, or as in the case o-f the Dultgen process both continuous tone and screen positive are used; (b) from the positive image a print is made on a gelatine coated paper known to the trade as carbon tissue; (c) this printed carbon tissue is then transferred by a squeegee method to the copper, and by immersion, orv other application of hot water, the backing paper usedl to support the gelatine is removed and the gelatine image developed; (d) when dry, this developed gelatine resist forms the base through which the image is etched into the copper, forming an intaglio printing surface.

There are several objections to the foregoing operation. No adequate means has been found to control the stretch and shrinking of the paper during color printing operations. This is the chief cause of misregister between color elements printed by successive impressions. Because of this gelatine coated paper, it has been impossible to use modern step and repeat machines for the preparation of printing surfaces by the intaglio or gravure method.

In accordance with the present invention,V the positioning and printing of the positive image is accomplished pho-tographically with a high degree of accuracy, the use 'of carbon tissue is eliminated and the modern step and repeat machine can be .used in the preparation of printing surfaces by the gnavure or intaglio process.

In the practice of my invention, the color separation negatives and positives are made in the usual way, and then printed on a specially prepared plastic or metal plate on which has been previously coated the gelatin which will, after exposure, be directly transferred from the plate to the copper printing surface. At this stage, the printed gelatine forms the etching resist.

I employ metal or plastic plates of preferably about l0/1000 thickness, smooth finished on one surface and formed with two register holes drilled or punched in the proper position. These register holes provide the means for later positioning the gelatin image in exact position on the printing surface.

These plates are then coated with a suitable `substratum to overcome halation of the printed image and to make stripping easily accomplished during transfer to the copper printing member, usually a cylinder, prior to etching. On this substratum a standard mixture of gelatin and pigment is coated, using a whirler or other suitable means. This gelatine and pigment can be sensitized before coating, or the plates can be coated and stored to be sensitized later. This plate on which the gelatin pigment has been coated eliminates any possible misregister due to shrinkage as in the case loi" carbon tissue. The plate can then receive the image. For example, it can be placed in a conventional step and repeat machine and accurately positioned duplicate prints of any number made. This would not be possible with .carbon tissue.

In the drawings, I have shown a transfer machine by which transfer of the printed gelatine from the metal or plastic plate may accurately be performed.

Fig. 1 is a front elevation of the transfer machine;

Fig. 2 is a detail perspective View of the plateholding frame with its pressure roller, a plate being shown held thereby against the surface of a printing roller which is` to receive the printed gelatine;

Fig. 3 is a side elevation of the machine;

Fig. 4 is a purely schematic View, being a section showing the pressure and printing rollers, and the gelatine plate therebetween to indicate the stripping of the printed gelatine, the slide carrier for the plate having been omitted from the view; and

Fig. 5 is a fragmentary elevation showing one side portion of the frame and its reception of a guide lug carried by the plate.

In the following description the plastic or metal plate carrying the gelatine-pigment layer will be termed the gelatine plate. Referring to the drawings, I have shown a frame consisting of the base member l, side frame members 2, and transverse connecting member 3. Mounted on the flanged front of each side frame member 2 is a slide 4 formed with a bearing boss .4m for a transverse shaft 5 which carries a pressure roller 6 which may be of hard rubber.' Forwardly depending arms 4mm, one carried by each slide 4, may be connected by la `oar 1, and to this bar may be connected the lowerV .endso-f chains 8 led over the idler sprockets 9 to counterbalance weights I9. The sprockets can be carried on a shaft II (Fig. 3) held by bracket arms I2 carried by the side frame members.

Each slide 4 carries. an upwardly .projecting screw I3 in such manner that the latter is held against .endwise movement. Each screw I3 passes through the aperture of a boss i4 carried by an appropriate one of the two brackets l2 and thence extends upwardly into a gear box I5 in which is an internally threaded gear (not shown) into which is received one of the screws I 3. Any suitable driven means may be employed to rotate internally threaded gears which will be held against endwise movements and rotated u ends of compression rollers, are apertured hanger risers 91: of frame members 2li which frame members may be held in parallelism by cross bars at their ends, suchas cross bar 205cm shown in Fig. 2. The framemembers mayk directly abut the compression roller as in Fig. .2, or may be held spaced therefrom as in Fig. Each frame member 29 is formed with a horizontal flange 20w cut with a longitudinal V groove.

The gelatine plate 2! is formed with registration holes. as in its corners, to receive pinsf2lzr on a slide carrier 21m. The slide carrier preferably is formed at its lower side margins with longitudinal wedge projections to be received in the said guiding grooves of the frame.

The space between .the compression roller 6 and the flanges 20x of the frame members will be such as to admit the inner areaof the slide carrier 2 and the gelatine plate through such space for free sliding movement on the frame 20.

Below shaft 5 is a second shaft, 22, journaled in bearing bosses 23 carried by the main frameZ. This shaftis quickly removable and has ,a squared or vkey connection with the hub of an independently mounted worm wheel 24 driven by a worm V25 on a shaft 26 driven by suitable connections Shaft 22 can be driven by bevel transfer of the printed gelatine to the copper cylinder or other printing member may be rubber cement or any other suitable material of a nature to readily free the gelatine from its said carrying plate.

When the gelatine plate has been printed it is applied to the undersurface of the slide carrier ZI, and in exact registration because the pins 2I$c of the slide carrier will enter the registration holes of the gelatine plate, and the latter will be held in such manner that the gelatine faces the copper cylinder 28.

Water is applied to the surface of the copper cylinder precedingthe downward movement of .the pressure roller 5, by the instrumentalities above described, until rm but controlled pressure is imposed upon the gelatine plate. This wetting of the copper cylinder plus the pressure causes the printed gelatine to be stripped from the metal or plastic plate as it passes through the machine. As hereinabove described this last operation is performed by rotation of shaft 22 and the copper cylinder itself.

The metal or plastic plates can be re-coated and used over again in the same manner.

After the transfer of the printed gelatine pigment from its plate to the copper cylinder, any trace of rubber cement is removed and development with hot water may proceed in the usual way, and then the gelatine resist may be dried, followed by etching to complete lthe preparation of the printing surface on the copper cylinder.

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

1. A machine adapted for' transferring gelatine pigment layers from carrierV plates therefor'and to printing cylinders, which comprises means for rotatively supporting a printing cylinder, means for rotating said cylinder, a pressure roller overlying said cylinder, means for raising and lowering the pressure roller, a frame intermediate the roller and cylinder and formed with guideways, a carrier mounted on said guideway for sliding movement in position to be directly engaged by the printing cylinder, and registration pins on said carrier for registration with apertures in a gelatine plate in such manner that the gelatine surface of the latter is held in contact with the printing cylinder.

2. A machine constructed in accordance with claim 1 in combination with screws carrying the pressure roller, power means for rotating said screws, and power means for rotating the printing cylinder, the carrier having ribs received in channels formed in the frame, and the frame having. co-axial .support with the pressure roller.

ROBERT MACKAY.

REFERENCES CITED The following references are of .record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,340,346 Horgan May 18, 1920 1,989,017 Neumann Jan, 22, 1935 2,030,731 Young Feb. 11, 1936 2,213,443 Huck Sept. 3, 1940 2,240,737 Hannon May 6, 1941 2,320,352 Ericksson June 1, 1943

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