Patent GB-876201-A (GB)
Title: Improvements in or relating to printing cylinders
Inventor: LUCK LEONARD
IPC: B41D3/08
Filed: 1957-06-04
Abstract: 876,201. Printing surfaces. ABELL, Sir G. E. B., LUCK, L., and CHADDER, H. L. Sept. 4, 1958 [June 4, 1957], No. 17772/57. Class 100(2) A method of producing an electrotype replica, for use as a printing surface, in the form of a circumferentially continuous sleeve, of a master sleeve or cylinder, comprises casting a mould around the master sleeve or cylinder and within a mould support or several mould supports, separating the mould and the master sleeve or cylinder, and electroplating the internal surface of the mould to produce an electrotype replica of the master sleeve. As shown the master sleeve 11 is of steel and bears intaglio design areas 12; the design surface being chromium-plated. A cylindrical mould support consisting of a number of metal segments 20 is erected round the master sleeve, an equal number of perforated metal reinforcing liner segments 13 being disposed in the annular space between the sleeve 11 and the mould support. The liner segments 13 have end flanges 14 which project radially outwards between adjacent mould support segments 20. Separators 16 are interposed between adjacent flanges 14 and can be adjusted radially with respect thereto by means of screws 17. The separators 16 and the internal surfaces of the segments 20 are chromium plated. The segments 20 are secured together and are mounted concentrically with the master sleeve 11 on a base plate 30. A plate 21 in the wall of each segment 20 is connected to the remainder of the wall by a plastic diaphragm 22 and can be moved radially by means of screws 23. The separators 16 are moved into contact with the master sleeve 11 and the plates 21 are fully withdrawn to provide maximum volume within the mould. A synthetic resin in liquid form is then poured into each compartment. Epoxide resins, polyesters or polyurethanes may be used. A cover plate 31 is then secured on top of the assembly and the resin is cured, pressure being applied thereto by means of the plates 21. After curing of the resin the segments 20 are. removed and the reinforced cast resin segments are separated. The cast segments are reassembled after removal of the master sleeve and the separators 16 are moved outwards a few thousandths of an inch. The small recess thus left at each segment join is filled with the same resin as is used for casting or a suitable organic cement, so as to produce a uniform surface on the matrix formed by the cast segments. A nickel coating, e.g. one tenth of an inch, is formed by electrodeposition on the interior of the matrix and subsequently copper is electrodeposited on the nickel coating to a depth, e.g. of one quarter of an inch. After the deposition the matrix segments are parted and the newly formed printing sleeve is chromium plated. The electroformed sleeve may be of nickel alone. In a modification the separators 16 are not used and the resin matrix, which is not reinforced, is cast in the form of a sleeve. The sleeve is expanded in a vacuum chamber to allow the master sleeve to be withdrawn and is reassembled, at its normal diameter, with the mould support segments which support it during the electrodeposition process.