Method and apparatus for counting sheets which may be fed in skewed

Abstract

Sensors in the infeed and output stackers, under control of the microprocessor, monitor the sheets. The apparatus is started automatically by placing sheets in the infeed. A count of the sheets is developed and displayed as the sheets are fed. When the infeed is empty and the output contains sheets, the count is retained. If sheets are removed from the outfeed, the count is retained and is reset only after more sheets are placed in the input. The same rules obtain for batching. The sensors cooperate with singles, holes and doubles detectors and have their gain adjusted depending upon sheet density. Automatic threshold adjustment circuits compensate for dust build-up and component aging. Upon sheet detection, the sensing circuit threshold level is instantaneously shifted to prevent an abrupt change in intensity from the sheet covering the sensor to provide an erroneous indication of the presence of a subsequent sheet or sheets. The sensors assure accurate counting even though sheets are fed in skewed and/or overlapping fashion. An amplifier normally in saturation is driven out of saturation when light intensity drops to increase the ability to determine the transmissivity to distinguish between single and double sheets. Operating speed may be reduced from normal speed. All timing is automatically readjusted according to the selected operating speed. The control circuitry may be coupled to and synchronized with a denominations counter and printer. The doubles detection circuit may also discriminate between two and three overlapped sheets.