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1470584 Moulding metal printing cylinders by isostatic compression MOHAWK DATA SCIENCES CORP 19 March 1974 [9 May 1973] 12202/74 Heading B5A [Also in Division C7] A printing cylinder having raised characters on its outer surface is formed by isostatic compression of metal powder in the apparatus shown in Fig. 1, in which an expandable bag 32 may be pressurized to compact metal powder against a compressible sleeve 40 having character depressions 49 formed in its inner surface, the sleeve 40 being supported by rings 34, 38 and 42 between upper and lower rams 14 and 16 and an outer metal enclosure 20. A support cylinder 26 within the expandable bag 32 has bores 47 for the supply of pressure fluid 48 (glycerine) to the interior of the bag, via a bore 22 in the lower ram 16 and hydraulic pressure multiplier 52, from an hydraulic pump 54. To form the printing cylinder, the mould 18 comprising parts 26, 32, 34, 38 and 40 is removed from between upper and lower rams 14, 16, and filled with metal powder, filling being facilitated by vibration. The top ring 42 is then placed on the mould 18, which is then positioned between rams 14, 16 and lowered into enclosure 20. The metal powder is precompressed using the upper ram 14, after which the bag 32 is pressurized to assist compression, the pressure produced by the ram 14 being maintained higher than that produced by the bag 32. The mould and compacted metal drum are then removed by raising ram 16, and the mould disassembled to give the drum still inside the ring 38 and sleeve 40. The drum is machined, whilst still inside the ring 38, to the required internal diameter. The drum and sleeve are then pushed out of the ring 38, and the sleeve 40 removed from the drum by cutting. Before sintering, a mounting core which has also been produced by isostatic compaction of metal powder is inserted in the drum, and the whole sintered to give the final cylinder. As described with reference to Fig. 3, not shown, the character sleeve 40 may be produced by injection moulding of a glass fibre filled polyurethane composition.
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