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(11) | EP 0 853 258 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A sheet transport system |
| (57) A sheet feed sensor (116) 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 (118) of the sensor (116) 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 (116), 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 (116) is in the second given voltage response condition. This way
the difference between a voltage response at the phototransistor for a single sheet
and a voltage response for two sheets, each of the same paper weight as the single
sheet, fed through the sensor is large enough throughout all paper weight ranges to
obviate the possibility of voltage response overlap. |