Patent GB-841510-A (GB)
Title: Improvements relating to offset printing
IPC: B41L11/00
Filed: 1958-05-29
Abstract: 841,510. Printing-machines. ADDRESSOGRAPH-MULTIGRAPH CORPORATION. May 29, 1958 [June 17, 1957], No. 17162/58. Class 100(2) An offset printing machine comprises a forme cylinder adapted to carry a lithographic master, an impression cylinder, a blanket cylinder interposed between the forme and impression cylinders to transfer an ink image from a master mounted on the forme cylinder to a print receiving sheet positioned between the blanket and impression cylinders, means for mounting a first blanket in fixed position upon a given portion of the external surface of the blanket cylinder, means for mounting a second blanket upon a different portion of the external surface of the blanket cylinder, means for advancing the second blanket along the surface of the blanket cylinder, and drive means for engaging the advancing means to actuate the advancing means to move the second blanket through a predetermined distance upon occurrence of one or another preselected number of printing cycles. As shown, sheets fed from a feed table 28, Fig. 2, are printed between an offset cylinder 26 and an impression cylinder 27. A planographic master sheet, mounted on a cylinder 25, is inked by rollers 35, the master also being supplied with ink-repellent by a roller 38. The cylinder 26 has a fixed blanket 92, Fig. 4, and a movable blanket 93 having its ends joined by a clamp 97. The blanket passes between a feed roller 98 and a spring-pressed pressure roller 99, around an idler roller 111, and around a tensioning roller 112-. The roller 98 is mounted on a shaft 118 carrying pinions 119, 121, Fig. 5, engaging pinions 120, 124 on the shaft 113 of the pressure roller 99 and on a stud 123 respectively. A ratchet 125 is secured to the pinion 124, while a ratchet lever 126 carrying a pivotally mounted pawl 130 is pivotally mounted on the stud 123. The lever 126, Fig. 7, is rocked towards a stop 128 by a spring 129, while a spring 132 rocks pawl 130 towards wheel 125. A plunger 134, Fig. 5, slidably mounted in a bush 144 secured to the machine frame 22, is urged outwardly by a spring 145. The plunger 134 may be pushed inwardly to the operative position, Fig. 10 (not shown) by a pivotally mounted handle 146 having a cam surface, the handle being secured to a bell-crank lever 147, Fig. 11 carrying a cam follower 150 engaging a cam 149. When the plunger 134 is in operative position (Fig. 10, not shown) it intercepts the path of the lever 126, Fig. 7, thereby causing this lever to pivot about the stud 123 to allow rocking of the pawl 130 from the stop 128. The pawl 130 is thus allowed to engage the ratchet'125 to rotate the gear 124, thereby rotating rollers 98, 99, and so advancing the blanket 93. A blanket reset mechanism comprises a knob 154, Fig. 11, secured to a shaft 155 rotatable and axially slidable in a bracket 152 fixed to the frame 22, the knob being urged outwardly by a spring 157. The knob is pushed inwardly and rotated in either direction to feed the blanket forwards or backwards through a pinion 156 engaging a pinion 159 on a shaft 158 which rotates the shaft 118, Fig. 5, of the roller 98 through a socket 160 (Fig. 13 not shown). The position of the tensioning roller 112, Fig. 4, is adjusted by rocking an arm 141 (Fig. 6, not shown) on a shaft 140 Fig 4 carrying arms 139. The arms 139 carry rollers 138 which engage slidable blocks 136 supporting the shaft 135 of the roller 112. The arm 141 is rocked by varying the setting of an eccentric 142 (Fig. 6 not shown). In operation, a master carrying repetitive and variable data to be produced is mounted on the cylinder 25. The handle 146 is set to inoperative position such that the movable blanket 93 remains stationary. Thus, the repetitive data such as heading matter 181 (Fig. 14 not shown) is transferred via the fixed blanket 92 to a sheet, card &c. fed from the table 28, while variable data 182 (Fig. 14, not shown) is transferred via the blanket 93 to such sheet &c. If only selected items of the variable data are required for printing the blanket 93 may be moved into an appropriate position by depressing the handle 146, Fig. 5, thereby causing the blanket to be advanced a predetermined length upon each revolution of the cylinder 26. The sheet used for such variable data is only long enough to carry the repetitive data and the lines of variable data required. If desired, each line of variable data 182 (Fig. 14, not shown) may be reproduced successively on the sheet, fed by maintaining the handle 146 in operative position.