GB631010A - Improvements in sheet printing - Google Patents

Abstract

631,010. Printing-machines. HOE & CO., Ltd., R. June 16, 1947, No. 15864. Convention date, June 14, 1946. [Class 100 (ii)] In a rotary multi-colour printing-machine errors of register due to change in width of the trailing part of a sheet which is gripped by its leading end are prevented by warping the leading end of the sheet as it is advanced to printing position, the warping being produced by bowing the gripper bar. In one form in which the sheets are carried through offset printing couples by grippers 6 mounted on gripper bars 5 carried by supports 10, Figs. 4 and 7, on chains 1 as described in Specification 478,362, the grippers being received in recesses 20 in the impression cylinders 12, the gripper bars are supported at one side by rollers 31 mounted concentrically on a shaft 32 secured in the recess 20, and on the other side by rollers 33 mounted eccentrically on a shaft 34 which extends through the end of cylinder 12 as shown in Figs. 7 and 8, and is connected to a sector 40 having means for adjusting and locking it in positions determined by a pointer and indicator scale 44. The rollers 33 can thus be set to positions indicated by full and dotted lines in Fig. 8, or in intermediate positions, and thus cause a bowing of the gripper shaft to give a forward or rearward movement to the centre of the printed sheet and thus correct errors of register due to slight warping of the sheet in directions causing widening or narrowing of the trailing part of the sheet. In a modification, Fig. 11, as applied to a machine in which sheets are fed to the impression cylinders 104, of a multi-colour offset press by means of transfer cylinders 103, Fig. 9, not shown, means are provided to bend a gripper bar 110 at its centre in an upward or downward direction depending upon whether the printed sheet tends to increase or decrease in width. The bowing movement is dependent upon the setting of a pin 137 concentric to, or on either side of, the pivot of an arm 140 which is oscillated at each rotation of the cylinder 104 by means of a roller 150 which moves over a fixed cam 152. The pin 137 can be moved in a slot 143 in the lever 140 and a scale is provided to aid the setting of the pin. In either form, means may be provided for adjusting the bowing of the gripper bar while the press is running. As applied to the conveyer type of press this may be effected by adjusting a stationary cam over which rolls a roller on a lever arm which adjusts the eccentric rollers 33, Fig. 8, as grippers pass over the impression rollers 12.