GB1302079A - - Google Patents

Abstract

1302079 Control device for machines handling stacks POLYGRAPH LEIPZIG VEB 2 July 1970 32041/70 Heading B8C A control device in a machine handling stacks 4 of sheet material, e.g. paper, cardboard, comprises a first normally closed switch 1 and a second normally open switch 2 connected in series in a control circuit 3 so that the latter is only completed and a machine operation initiated when the trailing edge of the stack has passed the switch 1. As the stack 4 approaches the switches 1, 2 along a path 8 (Fig. 1, part I), its leading edge contacts a first sensor 9 to open the switch 1 and then a second sensor 10 to close the switch 2 (Fig. 1, part III), the switch 1 being reclosed to complete the circuit after the trailing edge has passed (Fig. 1, part IV). The sensors 9, 10 may comprise levers or the beams of photoelectric devices (15, 16, Fig. 2). A change-over switch (5, Fig. 3) may be incorporated so that a machine operation may be effected as above or by the leading edge only of the stack actuating the switch 1, switch 2 being redundant.