ES337650A1 - Improvements in or relating to Duplicating Machines - Google Patents

Abstract

A rotary duplicating machine comprises a rotatable printing cylinder with attached master sheet, a sensing device for a copy sheet which controls an A.C. electromagnet, mechanical linkage actuable by the electromagnet to release the printing cylinder for rotation and means for rendering the electromagnet inoperative before it has completed one revolution after release. Fig. 1 illustrates a rotary duplicator in which a copy sheet 1 is fed over feed table 3 to a moistening device 4, and then between feed roller 6 and stop-pin 5 to the impression roller 28 in contact with printing drum 20. When the paper sheet slides over part 10 of a sensing lever 2, the latter is pressed into a groove in the feed roller 6 (Fig. 2, not shown), while rocking movement of the lever 2 about bolt 9 closes the switch spring of microswitch 11 by means of part 35 of the lever closing of switch 11 actuates electromagnet 12 which attracts plate 14 in the direction of arrow A, rocking release member 13 about pivot 15 in the direction of arrow B. The movement of the release member 13 allows drive pawl 17 to rock about its pivot 18 under tension from spring 25 and engage in a nose of the drive wheel 24. Since the drive wheel 24 is fixed to motor-driven drive-shaft 19 and the drive pawl 17 is fixed to the printing drum 20, the drum 20 is then driven by the continuously rotating drive wheel 24. Cam 26, also fixed to the drum 20, rotates, and after part of a rotation comes out of engagement with switch 27 which opens, cutting off the circuit to the electromagnet through a system of relays (Fig. 3, not shown). The release member 13 rotates about its pivot 15 under tension from spring 16 back to its basic position, and after one rotation of the printing drum 20, lifts drive pawl 17 out of the nose of the driver wheel 24, and disconnects the drive ready for the passing of another sheet 1 over sensing lever 2 which has been rocked back to its initial, contact-breaking position, under the influence of weight 34. An alternative embodiment (Figs. 4-5, not shown) includes a switch (46) which is actuated by movement of the release lever 13 and through a system of relays renders the electromagnet inoperative in this case, switch 27 is closed when cam 26 has gone through part of a rotation, and through a further circuit, prepares the necessary relays for passing of the next sheet over the sensing lever. A direct contactor circuit may be provided for the electromagnet, in which the circuit runs from the electromagnet through a carbon brush to the stop-pin 5, via the sensing lever (53) and cable (51) back to the magnet (Fig. 6, not shown), flow through the circuit being interrupted by the sheet feed. Over-riding switches (Figs. 7 and 8, not shown) may be incorporated in the circuits when the normal operation, i.e. through sensing lever 2 and switch 11, is not required. In particular, a lockable hand-switch can be incorporated in the circuit to keep the electromagnet operative during automatic feeding of a stack of sheets, thus enabling the printing drum to rotate continuously until the last sheet is fed or until the hand-switch is unlocked.