| 摘要 |
1367255 Proximity switch LA CELLOPHANE 13 March 1972 [15 March 1971] 11685/72 Heading G1N Variations in electrical characteristics of a corona charging device of an electro-photographic copying machine due to a sheet of paper inserted therein are used to switch on auxillary components of the machine. A high discharge voltage from generator G is connected across electrodes B, B' each including a pair of parallel conductors F, F or F, F' surrounded by earthed screens E, E'. When a sheet of paper indicated by dashed line is passed into the device between electrodes B, B' the capacitance and hence leak resistance between the two electrodes increases resulting in an increase in potential drop across B, B'. This has the effect of increasing the leakage currents flowing between the electrodes and their respective screens E, E' so that the potential at point A rises to trigger on thyristor T and energize relay L to close switch K and complete the supply circuit to the lamps of the machine. Capacitor C maintains the relay energized during the negative half cycle of the supply when the thyristor is non-conducting.
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