EP0133328B1 - Perfecting rotary multicolour printing machine - Google Patents

Abstract

The machine can print on one of the paper sides an image with juxtaposed colors by means of a typographic plate cylinder inked by a collecting cylinder inked in turn by selective color inking cylinders of which the number corresponds to the number of colors, and on the other side an image with superposed colors and designs by means of offset plate cylinders contacting an offset blanket cylinder and of which the number corresponds to the number of colors and designs of this image. For this purpose the machine comprises another blanket cylinder contacting the typographic plate cylinder and pressed against the offset blanket cylinder, the paper passes between this cylinder and the other blanket cylinder. The multicolor printing on the side receiving the image with juxtaposed colors may be completed by a monochrome wet offset print.

Description

The invention relates to a multi-color rotary printing machine for double-sided printing according to the preamble of claim 1.

Such a machine is known from DE-A-2 115 790 and comprises a plate cylinder which is inked directly by color picking cylinders, the number of which corresponds to the number of colors in the image to be printed. Each selector cylinder has areas cut in relief representing the parts of the image to be colored in a determined color which its own inking device has transferred to it. The plate cylinder is in contact with a collecting cylinder constituted by a blanket cylinder which has only the function of balancing the inks on the printing plates fixed on the plate cylinder. In addition, the plate cylinder is in pressure against the offset blanket cylinder itself inked by offset plate cylinders and in pressure with a back pressure cylinder. The paper passes first between the offset blanket cylinder and the back pressure cylinder to obtain a multicolored offset printing on one side, then between the offset blanket cylinder and the plate cylinder on the printing side collector to obtain a collector impression on the other side. Since in this known machine, on the collector printing side, the plate cylinder is in direct contact with the color selector cylinders, the color selector plates carried by these must be made of less hard material than that of the printing plates, this limits the fineness of the dimensions of the reliefs and therefore the fineness of the design which can be obtained. In addition, there are two different printing sites, said printing therefore being done successively.

Furthermore, we already know, from German patent application DE-A-3 109 964 a printing machine ensuring on one side of the paper the printing of an image in juxtaposed colors. This image is printed by means of a single typographic printing plate representing the complete drawing to be printed and mounted on a plate cylinder. This typographic plate is inked by a collecting cylinder formed by a blanket cylinder which is in turn inked by a plurality of color selector cylinders. The plate cylinder carrying only one letterpress printing plate has only a small diameter adapted to the dimensions of this single letterpress printing plate. The paper passes between a second blanket cylinder which is in contact with the typographic plate cylinder and has the same small diameter as the latter, and a back pressure cylinder.

In the same document DE-A-3 109 864, a symmetrical version of this machine is described for carrying out simultaneous two-sided printing. In this version, the back pressure cylinder is eliminated and replaced by a symmetrical arrangement of the cylinders with respect to the mentioned machine, comprising a third small blanket cylinder in contact with the second blanket cylinder, another cylinder typographic plate and another collecting cylinder in contact with other color picking cylinders inked by inking devices. The paper passes between the second and third blanket cylinders.

This machine is used in particular to print the security background for banknotes.

This process, which is commonly called "Orlof" or also color collection printing, gives a multicolored image ensuring a perfect register between the different colors of the drawing of the image, a result impossible to obtain with any other printing process. Since the color selector cylinders are in contact with an elastic surface of the collecting cylinder, they can be made of hard material which makes it possible to cut out very fine raised areas, therefore very fine colored parts, for example in the form of lines or dots.

On the other hand, indirect typographic or offset printing with colors and overlapping designs is known which, too, is often used to print security funds. According to this method, the complete drawing is composed of partial drawings of different colors carried by offset printing plates mounted on plate cylinders so as to allow the superimposition of drawings and colors in register with each other on a cylinder blankets against which the paper to be printed is pressed. The number of offset printing plates and, consequently, of plate cylinders corresponds to the number of different colors and designs composing the multicolored image.

There are also machines of this type for simultaneous two-sided printing in which the paper passes between two blanket cylinders, each receiving a multicolored image of the corresponding offset plate cylinders.

The object of this invention is to create a single machine, in an improved configuration, which combines in simultaneous two-sided printing the two methods described above and hereinafter called the "Orlof" method and the offset method.

To achieve this goal, the machine is characterized by the characteristic clause of claim 1.

The advantage of this machine is that it makes it possible to use at the same time two completely different processes for printing in a single pass simultaneously an offset image on one side and an "Orlof" image on the other side, which offers the user for the first time the possibility of printing, in particular, security funds on both sides of a bank note by two different processes; this increases security against forgery and also makes printing operations more economical because the user does not have to use two separate machines.

Advantageous embodiments of the invention are described in the dependent claims.

The invention will be described by way of nonlimiting example by an embodiment and a variant with reference to the accompanying drawings.

Figure 1 schematically shows a printing machine according to the invention.

FIG. 2 schematically represents, in partial view, an extension of this machine supplemented by another wet offset printing unit.

The machine shown relates to a sheet printing machine and comprises a sheet-type paper input device 1 provided with a margin cylinder 2, two transfer cylinders 3 provided with clamps, and dust removal devices and elimination of static electricity 4 and 5 installed on both sides of the paper 1. The sheets are transferred to a blanket cylinder 12 provided with clamps and pressurized against another blanket cylinder 13 of the same diameter. The sheets pass between the blanket cylinders 12 and 13 and are printed simultaneously on both sides. The cylinders rotate in the direction indicated by the arrows. After being printed, the sheets are transported by a chain clamp system 21 on output stacks or, if necessary, to a machine to complete the printing. The main engine of the machine is designated by 22.

The blanket cylinder 12 cooperates according to FIG. 1 with four offset plate cylinder, three of these offset plate cylinder 8 are equipped, in the example considered, each with a dry offset printing plate each inked with an inking device 7 with double inkwell; the fourth offset plate cylinder 11 carries a wet offset printing plate inked by an inking device 9 with simple inkwell and provided with a wetting device 10. All these elements 7 to 11 are installed on a movable carriage d offset 6.

Dry offset printing plates are typographic plates known per se and the wet offset printing plate is a hollow plate also known per se. These four offset plates represent partial drawings which are inked in different colors and the number of which corresponds to the number of colors and drawings of the first image to be printed on one side of the paper 1. This image is in particular a security background in the case fiduciary papers, in particular banknotes.

These partial drawings of different colors are brought together on the blanket cylinder 12 functioning as an offset blanket cylinder, therefore as a collecting cylinder for the partial drawings composing the multicolored image. This image is transferred to one of the sides of the paper, in the example considered on the back side, where a dry offset printing in three colors is thus obtained, supplemented by a monochrome wet offset printing.

In the case of fiduciary papers one can also use the three dry offset plate cylinders 8 to create a background in three colors, while the wet offset plate cylinder 11 represents a main design.

Of course for offset printing all the plate cylinders mounted on the movable carriage 6, therefore in the example considered all the four plate cylinders can also be fitted with dry offset plates.

On the other side of the machine are the elements to produce an "Orlof" image. These elements include a blanket cylinder 17, which has the same diameter as the blanket cylinders 12 and 13. This blanket cylinder 17 cooperates in the example illustrated with four color selector cylinders 16 having reliefs cut according to the contour of the areas to be printed in the respective color, they are inked in said color, each, by means of an inking device 15 with double inkwell. These elements 15, 16 are installed on a mobile "Orlof" inking carriage 14. These selector cylinders 16 are preferably made of hard material which does not risk deforming even if the relief is very fine, thus making it possible to obtain a security background made up of very fine colored areas. The areas of the four colors are transferred to the blanket cylinder 17 which functions as a collecting cylinder on which they are joined and by which they are transferred to a plate cylinder 20 carrying a letterpress printing plate in contact with said collecting cylinder and with the blanket cylinder 13. This typographic plate represents the complete drawing of the second image to be printed in four colors on the other side of the paper. The complete image inked in the different colors is in turn transferred to the blanket cylinder 13 to apply the printing of the complete image, in particular a security background, on the front side of the paper, the back side of which receives simultaneously the offset image. During the simultaneous printing the two cylinders 12 and 13 serve mutually as back-pressure cylinders.

The machine further includes a first image transmission cylinder 18 and a second image transmission cylinder 19 which transfer the same image of the colored areas of the blanket cylinder 17 in perfect register on the typographic plate cylinder 20, thus making it possible to strengthen the inking of the letterpress plate in the desired colors and therefore to better cover these areas with the desired ink. Indeed, given the direction of rotation of the blanket cylinder 17, part of the ink is transferred by the cylinders 18 and 19 onto the typographic plate cylinder 20, during that the rest of the ink is transferred in perfect register directly to this cylinder 20. The arrangement of the cylinders concerned to obtain this double inking is known (DE-A-3.109.964), the second inking being offset by the length of the periphery of the typographic plate cylinder 20 or in the example considered one third of the periphery of the blanket cylinder 17 because the latter has a diameter three times larger than the diameter of the cylinder 20 and carries three blankets .

In order for this register condition to be fulfilled, the arrangement of cylinders 17, 18, 19 and 20 is such that the sum of the arc lengths on the peripheries of cylinders 18, 19 and 20 between the respective contact points - seen in the direction of rotation of these cylinders-must be equal to the length of the arc on the periphery of the cylinder 17 between the points of contact of the latter with the cylinders 18 and 20 plus 1/3 of the periphery of this cylinder 17.

If the design carried on the typographic plate for the "Orlof" printing is composed only of lines, therefore very narrow inked areas, one can give up the image transmission cylinders 18 and 19 and limit oneself to an inking simple of the typographic plate "Orlof".

In the example illustrated the ratio of the diameters of the cylinders 8, 11, 16, 18, 19, 20 on the one hand and of the cylinders 12, 13, 17 on the other hand is 1: 3; the periphery of the cylinders 12, 13 and 17 therefore corresponding to three sheets of paper, these cylinders each carry three blankets.

In the example according to FIG. 2 the printing according to the "Orlof" process is completed by a wet offset printing also carried out when the paper passes between the blanket cylinders 12 and 13, and which is used in particular to print a main design value paper monochrome. The wet offset unit comprises a hollow plate cylinder 23 provided with an inking device 24 and a wetting device 25, known per se, this hollow plate cylinder 23 cooperating with the cylinder blankets 13 which transfers the image to the paper. Therefore, in this case, a complete printing is obtained in a single pass on the front side, for example the security background in four colors by a printing according to the "Orlof" process and the main monochrome drawing by a wet offset printing, during that the back side receives the security background in four colors by an offset printing or a background in three colors and also a main monochrome drawing by a wet offset printing.

The machine described can be used without problem as a reel printing machine by simply replacing the means of transporting sheets by means of transporting a strip of paper which passes between the cylinders carrying the branches 12, 13.

Claims (3)

1. Combined rotary multicolor printing machine for recto-verso printing of a web or sheet, notably for printing the safety background of fiduciary documents, comprising

-a first blanket cylinder (12) contacting a plurality of offset plate cylinders (8, 11) each inked by an inking device (7, 9) in a different color and of which the number corresponds to the number of colors and designs of the first image to be printed on one side of the paper (1), the diameter of the first blanket cylinder (12) being a whole multiple of that of the offset plate cylinders (8, 11);

-a second cylinder (13) being pressed against the first blanket cylinder (12) the paper (1) passing between these two cylinders (12, 13);

-a third blanket cylinder (17) operating as a color collecting cylinder in contact with a typographic plate cylinder (20) representing the complete design of the second image to be printed on the other side of the paper (1), and

-a plurality of selective color inking cylinders (16), each being inked by an inking unit (15) in a different color, the number of said selective color inking cylinders (16) of which the relief areas correspond to the portions of the second image to be colored in the various colors is equal to the number of colors of this image, said machine is characterized by the fact that

-the, selective color inking cylinders (16) are contacting the third blanket cylinder (17) that transfers the inked zones to the typographic plate cylinder (20),

-the second cylinder is likewise a blanket cylinder (13) that contacts the typographic plate cylinder (20) and receives from this plate cylinder the second image, and

-the diameter of the second blanket cylinder (13) is the same as that of the first blanket cylinder (12) and is a whole multiple of that of the offset plate cylinders (8, 11).

2. Machine according to claim 1, characterized by the fact that at least one (11) of said offset plate cylinders carries a web offset printing plate with which a dampening device (10) is associated, whereas the other offset plate cylinders (8) carry dry offset printing plates.

3. Machine according to claim 1 or 2, characterized by the fact that it further comprises an offset printing unit, preferably a wet offset unit (23, 24, 25), of which the plate cylinder (23) contacts the second blanket cylinder (13).

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