Patent GB-1047222-A (GB)
IPC: B41L39/00
Abstract: 1,047,222. Rotary litho-offset printing machines. BLOCK & ANDERSON Ltd. April 24, 1963 [Jan. 24, 1962], No. 2679/62. Heading B6C. Selective line printing is effected in a rotary lithe-offset printing machine by dividing at least a part of the circumferential peripheral surface of the blanket cylinder into a number of separate printing segments all disposed parallel to the cylinder axis and each of which is faced on its outwardly directed surface with a layer of blanket material and is movable radially between an inward inoperative or non-printing position and an outward operative or printing position. The machine shown comprises printing, blanket and resiliently mounted impression cylinders 10, 20, 32 and inking and damping rollers 12 all mounted between two parallel frame plates 11. The circumferential peripheral surface of the blanket cylinder 20 comprises a plain tensioned section 27 and segments 13 of T cross-section and each corresponding to a line width of printing matter. As shown in Fig. 3, each segment covers half the length of the cylinder-and is in axial alignment with its " twin "-and all are axially and radially slidably supported at their ends in grooves in cylinder end plates 15. the latter being secured to the body of the cylinder. This is carried upon ball bearings 16 mounted on a fixed and partly tubular axle 17 which is rigidly secured at each end to a frame plate 11. All these segments are biased inwardly by springs 18. The mechanisms of Specifications 900,117 and 907,212 are modified and used as the means to pre-select the segments 13 which are required to print at any given time. Each segment B has a web 14 on its inner edge with a pair of spaced projections 19 while at the right-hand side of such projections is formed a recess 21. When in their normal axial position (Fig. 3) the recesses 21 are in alignment with each of two pairs of abutment rollers 22, 23, each rotatably mounted within pairs of parallel support plates 24, 25 which are non-rotatably mounted upon the fixed axle 17. When, however, any pair of aligned segments is displaced to the right, the rollers 22, 23 then align with the projections 19 and, upon engagement therewith during the rotation of the cylinder as a whole about the fixed axle, operate to displace the related segment radially outwardly against the action of the springs 18 to the outward, operative position as shown in xd in Figs. 1 and 3. The support plates 25 are rigidly connected to the fixed axle 17 but the support plates 24 are slidable axially along the axle 17 by a rod 26 whereby the associated rollers 22, 23 carried thereon may be moved so far to the right that even when the selected left-hand segments are displaced by the pre-selection means the projections 19 still fail to align with such rollers. As a result of this, the left-hand segments are left in the inward inoperative position during rotation of the cylinder and any printing is restricted to the right-hand half of the cylinder as is required for certain applications where part of the master image, such as price columns, need to be omitted from the copies. As shown in Fig. 1, the rollers 22 are so mounted whereby any axially displaced segment 13 is moved radially outwards to contact the master cylinder 10 as it approaches the common plane of the axes of cylinders 10 and 20 and is then moved radially inwardly again as it leaves the plane. In similar manner, the rollers 23 are so mounted such that the same axially displaced segments are each moved radially outwards towards the impression cylinder 22 and then inwards again. The copy sheets C.S. are fed into the bight between the cylinders 20 and 32 by sheet feed means comprising a roller 34 and a roller 35 intermittently rotated unidirectionally through mechanism deriving motion through cams from the printing cylinder 10 such that no sheet grippers are required, the tractive forces emanating from the friction between the outwardly displaced segments and the cylinder 32. Copy sheet retention in the bight when not gripped by contacting segments and cylinder is assisted through the provision of friction pads or balls or rollers at the entry zone to the bight. In a modified machine an ordinary impression cylinder with copy sheet grippers is used but the cylinder is locked against rotation and modified so as to mount rollers equivalent to the roller 34 and the cylinder 32. In yet another modified machine the conventional impression cylinder is rotatable but has no driving connection with the blanket cylinder 20. The separate roller and cylinder such as 34 and 32 are not provided but the usual sheet grippers are retained and used. This impression cylinder is then provided with friction brake means which operate to arrest it whenever it is not being driven by the feed roller 35, operative segments 13 or section 27.