Abstract: A single tray or multi tray sheet feed system is provided. A sensor is provided to sense the sheets leaving from the single tray or multi tray system. If the paper weight of sheets of paper on a tray fall within a first range of paper weight values, the sensor is designed to have a first given voltage response condition for sensing these sheets and if the paper weight of the sheets falls within a second range of paper weight values the sensor is designed to have a second given voltage response condition for sensing the latter sheets. A current value supplied to the emitter of the sensor can be controlled to provide the desired voltage response or a resistance in a phototransistor collector circuit can be varied to provide the desired voltage response condition.

Abstract: A sheet feed sensor is designed to have a first given voltage response condition for sensing sheets within a first range of paper weight values and a second given voltage response condition for sensing sheets within a second range of paper weight values. A current value supplied to the emitter of the sensor can be controlled to provide the desired voltage response or a resistance in a phototransistor collector circuit can be varied to provide the desired voltage response condition. If the first range of paper weight values is lighter than the second range of paper weight values, the sensor, when in the first given voltage response condition, will have a voltage response, when sensing a sheet of a given paper weight, which is higher than the voltage response when the same sensor senses a sheet of the same paper weight, when the sensor is in the second given voltage response condition.

Abstract: The invention relates to an apparatus for detecting sheet misfeed from a tray having at least two sheets whose thickness differs from each other. The thickness of each sheet is detected as it enters into the tray and that value is placed in memory. The thickness of each sheet is detected as it leaves the tray and that value of each sheet is compared to the thickness value in memory for the same sheet when it entered into the tray. If the values match, then only one sheet has been fed from the tray. If the thickness value of the sheet as it leaves the tray is more that the thickness value in memory, then that indicates that more than one sheet has left the tray and a signal is produced which results in the sheet feed system being shut down to enable an operator to correct the situation.

Abstract: The thickness of a first sheet fed from each tray of the multi-tray sheet feeder is detected by a first sensor and a thickness value is placed in memory for that tray. Each sheet subsequently fed from the same tray is detected by the same sensor and the thickness value sensed is placed in memory and compared with the thickness value in memory for that tray. When a tray is reloaded, the thickness value in memory for the sheets previously loaded in the tray is erased and the first sheet fed from the reloaded tray is sensed and a thickness value for that sheet is placed in memory for the reloaded tray. After the thickness value of a sheet is sensed by the first sensor, the sheets enter into the intermediate tray. The thickness value of a sheet is detected by an outlet sensor as it leaves the intermediate sheet tray and that value is compared to the thickness value in memory which was detected for the same sheet by the first sensor.