GB1117973A - Multiunit printing presses - Google Patents

Abstract

1,117,973. Multi-colour rotary offset presses. HARRIS-INTERTYPE CORP. 22 April, 1966 [7 June, 1965], No. 17713/66. Heading B6C. A multi-colour sheet fed rotary offset press comprises a plurality of printing units the latter being grouped in pairs, each unit having its offset cylinder movable from the printing position. Manually operable means by which any of the offset cylinders may be thrown-off are located at the delivery table of the press. Using said controls a sheet fed through the press may be printed in one or any combination of colours. The apparatus shown comprises a four-colour lithographic press 10 having four successive printing units 11-14 each including plate, blanket and impression cylinders 15, 16, 17 and inking and damping mechanism 18, 19. Each sheet to be printed is gripped by fingers on the impression cylinder 17, printed in one colour in the associated unit and passed to the next unit by either a transfer cylinder 22 or a chain transfer mechanism 23. The printed sheets are discharged at a delivery table 29. Proof printing.-The press may be used for proof printing, i.e. printing sheets with only the colour and image of any one unit. It may also be used to print combinations of the colours to be printed in these units, e.g. the combination of colours printed in units 13, 14. It may further be used to print all the combinations of colours which include one unit and then print all the combinations which include the next unit. For example, first printing in units 11, 12, then in 11, 13, then 11, 14, then in 11, 12, 13 and so on. The actuating mechanism for the proof printing also ensures that any one blanket cylinder is not "thrown-off" for too long a period causing an excessive build-up of ink and dampening solution. Tripping arrangements.-The blanket cylinders 16 of the units 11, 12, 13, 14 are mounted in eccentric bearings and are actuated by lever and linkage means from cam arrangements for " throwing-on " and "throwing-off" " relative to the work flow. Each pair of blanket cylinders associated with a unit pair 11, 12 or 13, 14 are mechanically linked to effect sequential " throwoff " and " throw-on ". Air motors are employed to selectively move the blanket cylinders for proofing purposes. A sheet detector is used in connection with the sheet feeding mechanism to the first unit 11, the absence of a copy sheet causing automatic sequential " throw-off" of the blanket cylinders of the units 11 and 12. A separate photo-cell is used to detect the absence of sheet feed to the unit 13, such detection resulting in sequential " throw-off of the blanket cylinders of the units 13 and 14.