REMOVABLE MATRIX, FOR THE CYLINDERS OF ROTOGRAVURE PRINTING MACHINES, FOR THEIR FURTHER USE

Abstract: Process for producing metal matrixes (15) that can be removed from the mandrels (18) of rotogravure printing machines, with an electrolytic copper film (24), to be engraved, laid over the base (21) of the nickel matrix (15), there being interposed between them a separator product (23) so that, after use, said film (24) can be taken off the matrix and replaced by a new film for a fresh engraving, thus making possible reutilization of the matrix (15).

Description: Removable matrix, for the cylinders of rotogravure print¬ ing machines, for their further use The invention concerns the cylinders for rotogravure print¬ ing machines . In rotogravure work a cylindrical form is normally used to print the desired image by means of an engraving process during which tiny hollow cells are formed that receive the ink subsequently transferred onto paper. The surface in which said cells are made by various methods - traditional, autotypical, conversion, electronic or some other - is generally of perfectly smooth copper. This surface is obtained by galvanic deposition on steel cylinders and is generally given a chromium plated finish. For each new set of images the cylinders are processed by specialized engravers and then sent to the user who mounts them onto rotogravure printing machines. Bearing in mind the considerable size and weight of each cylinder as well as the great vulnerabili y of the surfa¬ ces either already engraved or to be engraved, big problems arise over transport and storage with related costs and capital tied up for the purpose. To overcome these drawbacks and lower costs metal cylindri¬ cal matrixes have been devised that can be slipped on and off the mandrels. The surfaces of these matrixes are of the same copper as that used for traditional cylinders for good engraving re- suits. Various means are resorted to for locking the removable matrixes onto the mandrels. The best known consists of having a set of holes bored in the mandrel and through these air passes and spreads between the surface of the mandrel and the matrix to allow the latte to be slipped on and its position adjusted. Once this is done the flow of air is cut off so that the matrix and mandrel are held firmly together. To remove the matrix the process is reversed. The old matrix is eliminated and replaced by a new one with different images for a new printing run. Considering the great different between the weight of the matrix, about 2 kg, and that of the cylinder, about 100 kg, a removable matrix clearly offers a big advantage compared with conventional cylinders. Running costs for corrections, balancing and maintenance are reduced, as well as those for staff and transport. Print quality is better with avoidance of adjusting movement or costly wasted materials. Even so, however, as the present market situation requires a greater variety of packaging materials, which in turn mean shorter printing runs, allied to the need for lower costs to increase competitivity , the fact that at present matrixes have to be thrown away after use represents a big loss and negatively influences the market. The above invention eliminates these drawbacks and offers other considerable advantages both practical and economic as will be explained below. Subject of the invention is a process for forming metal ma¬ trixes that can be taken off the mandrels of rotogravure printing machines, on which matrixes there, is a film of electrolytic copper for engraving purposes. The copper film is applied to the matrix and between one and the other there is a layer acting as a separator. The presence of the separator means that the film can be easily taken off when the image it carries is no longer neede A new film for a fresh engraving is then deposited on the matri The separator product consists of a solution of silver or of passivating substances such as chromates, bichromates or other The separator is preferably an aqueous solution of silver salt whose titre of silver lies between 0.1 and 0.7 grams/litre. The base of the matrix is preferably nickel. A film of copper is applied to the matrix and then the sepa¬ rator product . To remove the film of electrolytic copper from the matrix mechanical means are used, after which a new film is applied following application of the separator product. The new engraved film is then chromium plated or given ano¬ ther protective coating. This invention offers evident advantages. The big reduction in printing costs because of the matrixes being reutilizable not only constitutes a considerable savin compared with present methods but also ensures greater versa tility and flexibility. Even short runs become economic which better suits present market needs. The process described therefore makes possible a wider variety of printing at lower costs and of better quality than that obtainable using the conventional type of cylinder. Characteristics and purposes of the invention will be made still clearer by the following example of its execution illustrated by diagrammatically drawn figures. Fig. 1 A mandrel for rotogravure printing carrying a matrix subject of the invention, perspective view. Fig. 2 A matrix, as invented, perspective view. Fig. 3 The matrix on a mandrel while the engraved film is being removed . Fig. 4 The matrix on a mandrel after removal of the engraved film. Fig. 5 The matrix after formation of a new film to be en¬ graved . Fig.1 illustrates a cylinder 10 like that on a rotogravure printing machine. Said cylinder 10 comprises a mandrel 11, with pins 12, car¬ rying a removable matrix 15, subject of the invention, on which there are engravings 16 for an image to be printed on a run of a certain length. On the surface of the mandrel there is a set of holes (not shown in the figure for simplicity) that serve to create an air cushion between the mandrel 11 and the matrix 15 when the latter is being slipped onto said mandrel 11. Ha ing onc fitted the matrix on correctly the flow of compressed air is cut off and the matrix 15 will then cling tightly to the sur face of the mandrel 11. As can be seen more clearly in Fig. 2, the matrix 15 is formed of a nickel base 21 over which is laid a film 22 of copper . Over this copper film a product 23 is applied consisting of a solution of silver whose function is that of a separa¬ tor . Over this again another film of copper 24 is applied .by a gal¬ vanic process and, after engraving, this film is given a chromium plated finish 25. The presence of the separating agent 23 facilitates removal of the film 24. On completing the printing run the user turns on the com¬ pressed air in the mandrel 11 and removes the matrix 15 whic can be sent to the engraving department. At the department the matrix 15 is slid onto a mandrel 18, with pins 19, similarly provided with means such as air cush¬ ions or others, that facilitate this operation and then lock said matrix 15 in place. Mechanical means are employed by the engraver to detach the film 24 as may be seen in Fig. 3. The film 24 is shown with its edges 26 being separated. Fig. 4 illustrates the matrix 15 with its nickel base 21 and the first copper film 22 after removal of the film 24. A film 37 of galvanized copper can then be formed after ap plication of the silver solution to create the separator 36. Fig. 5 shows the matrix 15 completely renewed with the fresh film 37. Said ustrix can therefore be engraved as desired by the user, after which it is sent to the user for a new printing run . As the above invention has been described and explained as an example in no way limited to this and merely to show its essential features, it is understood that numerous variation may be made to it according to industrial, commercial or any other requirements and that further systems and means may be included in it without causing a departure from its sphere o use . It is therefore clear that the application comprises every equivalent use of the concepts and every equivalent product executed and/or in operation according to any one or more of the characteristics set forth in the following claims.

Claims: C l a ims 1. Process for producing removable metal matrixes ( 15) to mount on the mandrels ( 11, 18) of rotogravure, printing ma¬ chines, with an electrolytic copper film (24) to be engraved, characterized in that the copper film (24) to be engraved is applied to a base (21) with interposition of a separator pro¬ duct (23) so that when the engraving is no longer needed, sai film (24) can be easily taken off and replaced by a new film (37) ready for a fresh engraving. 2. Process as in claim 1, characterized in that the separator product (23) is a solu¬ tion of silver . 3. Process as in claim 1, characterized in that the separator product (23) is an aqueou solution of silver salts having a titre of 0.1 to 0.7 grams of silver per litre. 4. Process as in claim 1, characterized in that the separator product (23) consists of passivating substances such as chromates , bichromates or others 5. Process as in claim 1, characterized in that the base (21) of the matrix ( 15) is mad of nickel . 6. Process as in claim 1, characterized in that over the base (21) a copper film (22) is applied and over this the separator product (23). 7. Process as in claim 1, characterized in that to detach the engraved electrolytic copper film (24) from the base (21) mechanical means are use after which, having interposed a separator product (23), a ne film (37) is applied over said separator. 8. Process as in claim 1, charac erized in that a protective coating (38) is applied over the new engraved film (37). 9. Process as in claim 8, characterized in that the protective coating (38) consists of chromium plating. 10. Extractable matrix ( 15) for mandrels ( 11, 18) of roto¬ gravure printing machines, having a film (24) of electroly¬ tic copper to be engraved, characterized in that between the copper film (24) to be engraved and the base (21) a separator product (23,36) is laid, the purpose of said separator product .(23, 36) being to facilitate removal of said film (24) when the engraving on it is no longer needed, and its replacement by a new film (37) ready for a fresh engraving. 11. Matrix ( 15) as in claim 10, characterized in that the base (21) is made of metal. 12. Matrix ( 15) as in claim 10, characterized in that a copper film (22) is applied over the base (21) and over this film is laid the separator product (23, 36).

Inventors: GIORGIO ERMANNO, GIORGIO, ERMANNO
Applicants: GIORGIO ERMANNO, ROTOINCISA SRL, GIORGIO, ERMANNO, ROTOINCISA S.R.L.
Application year: 1993
Main classification: B41N3
IPC codes: B41N1, B41N3