GB698347A - Improvements relating to sheet feeding mechanism for printing machines - Google Patents

Abstract

698,347. Feeding sheets. SERVANTE, F. C., and OWEN, O. L. Dec. 19, 1951 [Dec. 19, 1950], No. 30936/50. Class 100(i) A sheet-feeding mechanism for a printing- machine comprises a sheet-gripping device movable in timed relationship with the operation of the printing machine and adapted to pick up the top sheet from a stack of sheets and move it forwardly to a front lay on the impression cylinder and retain hold of the sheet until a gripping device on the impression cylinder engages the sheet. As shown in Figs. 1, 4 the stack 14 is mounted in front of the impression cylinder 11, slotted arms 22 being pivotally mounted at each side of the stack on a fixed axle 23. Suction grippers 17 are mounted on a suction tube 18 which extends over the stack and is supported at its ends in blocks 26 sliding in the slots 25 of the arms. An arm 30 fast with the arms 22 has a roller 29 engaging a cam 27 on the shaft of the impression cylinder so that the suction grippers are raised and lowered in timed relation with the printing cycle. The blocks 26 are connected by links 37 to levers 35 mounted on a shaft 36 and joined by links 34 to arms 33 having rollers 32 coacting with cams 31. Springs 38 and 41 urge the levers in a clockwise direction as seen in Fig. 4. A guide plate 42 is disposed between the stack and the impression cylinder to guide the forward edge of the sheet under a gripper 16 on the impression cylinder. In operation the suckers 17 descend on the top sheet at a pivot distant from the impression cylinder and vacuum is applied by a cyclically operated valve. The suckers then lift the top sheet and move it towards the impression cylinder at a speed slightly greater than the peripheral speed of the cylinder so that the front end engages the front lays 15 and buckles. The buckling is assisted by a slight dishing of the guide plate 42. The grippers 16 then close on the sheet and the suction is cut off, releasing the sheet to be taken by the impression cylinder. Spring-loaded sliding members 46 guided on the alignment plate 43 of the stack have presser fingers 47 resting on the top of the stack. Cam means may be provided to raise the fingers 47 to allow the top sheet to be withdrawn. Alternatively. the loading spring 48 may be so light that the top sheet may be withdrawn automatically when the suckers are raised.