CIRCUIT ARRANGEMENTS FOR AUTOMATIC SHEET FEED CONTROL

1,204,628. Feeding sheets. DRUCKMASCHINENWERK PLANETA VEB. 24 Oct., 1968, No. 50479/68. Heading B8R. A control circuit for a sheet feed device comprises two sheet detectors, for sensing the presence of a sheet at the lay marks of a printing machine, connected to a logic circuit which switches off the feeder and blocks the feed in the event of a difference in the signals from the detectors (misaligned or slanting sheet), switches off the feeder and blocks the feed in the event of no sheet at the detectors and permits continued operation of the feeder with the feed unblocked if a correctly registered sheet is detected. The detectors, not shown, are each coupled via an individual amplifier 1, 2, to the input means of an anticoincidence element 10. A source of timing signals Xr controls the amplifiers and the output of the element 10 is coupled via AND-gate 11 to means for switching off the feeder. A signal X 1 is fed to gate 11 when the feeder is operating. Indicator device 13, 14 provides an output signal when the detectors sense the absence of a sheet which signal is fed to OR-gate 12 together with the signal from AND-gate 11. A further OR-gate 5 is connected to the detectors and a third input of this gate is connected to an output of OR-gate 12, an output of gate 5 is connected to means for blocking the sheet feed.