Patent GB-710872-A (GB)
Title: Improvements in offset rotary lithographic printing machines
Inventor: BRUNS HERBERT FREDERICK
IPC: B41L19/00
Filed: 1951-04-25
Abstract: 710,872. Printing processes. DITTO, Inc. April 25, 1951, No. 9654/51. Class 100 (2) Rotary offset machines; impression adjustments.-An offset lithographic machine, e.g., as described in Specification 710.871, is provided with a rotatable blanket roll 45 engageable with plate and impression surfaces 2, 8 respectively provided on spaced members 4, 5 and 10, 11 which are mounted for rotation and circumferential adjustment about a common axis 14 disposed parallel to the axis of the blanket roll, the plate and impression surfaces being concentric to the axis of rotation 'of the spaced members. As shown a cylindrical plate sector 2 is mounted on inwardly extending flanges 4, 5 provided with outwardly extending hubs 6 and outwardly projectirig bosses 7. The impression member is similarly provided with flanges 10, 11, hubs 12, and bosses 13. The hubs 6, 12 are seated on the shaft 14 and fixed thereto by means of clamping members 15, 16 through which bolts 17 extend. In the hub 6, however, a circumferentially elongated slot is provided so that whilst the impression segment 8 is fixed in relation to the shaft 14, the plate segment 2 may be moved relatively thereto. Adjustment is effected by a turnbuckle arrangement 19, provided with a control wheel 20. A spring 26 may be provided to take up any backlash in the turnbuckle. Secured to the bosses 7 on the flange 5 of the plate segment 2 by screws 27 is a ring gear 29 which is provided with a cut-out portion 30 through which the bosses 13 on flange 11 may extend. Meshing with the gear 29 is a driving gear 31 and gear 46 on the blanket roll. Thus, as the gear 29 is carried exclusively by the plate segment 2 adjustment of the latter relative to the impression segment does not affect the position of the image formed on the blanket roll but will adjust the position of the final image on the paper carried by the impression surface. The bosses 13 on the flange 11 serve as seats to support a cam ring 38 secured by screws 39 disposed in the cut-out portion 30 of the gear 29. The bosses 13 on the flange 10 support a second cam. These cams fixed with relation to the impression segment engage cam following wheels on a damping roll and inking roll so as to move them clear of the impression segment whilst allowing them to make contact with the printing plate sector. The impression sector 8 carries a strip 42 of mixture absorbing material and the blanket roll has a discontinuous surface so as to accommodate blots or smears of ink. Driving arrangements.-The driving gear 31 is mounted on a shaft 32 to which is fixed a pulley section 59. A second pulley section 61 is slidably mounted on the shaft 32, but rotates therewith owing to the action of pins 60 which extend from the pulley section 59 through pulley section 61. Powerful springs 64 urge the two pulley sections together. The section 61 is provided with a screw threaded extension 62 on which is screwed a cap 63 which also bears against the end of shaft 32. Thus by screwing up the cap 63 the pulley segments may be drawn apart and a V-belt 58 which runs between the segments will run over a smaller effective diameter thus reducing the driving ratio, the slack being taken up by pulley segments 52, 54, one of which, 52, is fast on the driving shaft of a motor and the other, 54, is slidably mounted thereon. A compression spring 56 urges the segments togther. to take up any slack owing to adjustment of the pulley sections 59, 61. The spring 56 is weaker than the springs 64 so that with pulley sections 59, 61 close together, pulley sections 52, 54 are forced apart. A knob 36 is rotatably mounted on the cap 63 and serves to allow manual rotation of the shaft 32 by means of the pins 60 and pulley section 59.