Xerographic charging apparatus with means to terminate the charging cycle when a predetermined charge is obtained

Claim 1

AN APPARATUS FOR CHARGING A XEROGRAPHIC PLATE INCLUDING A CORONA GENERATING DEVICE HAVING AT LEAST ONE CORONA DISCHARGE WIRE POSITIONED ADJACENT TO A XEROGRAPHIC PLATE TO IMPOSE AN ELECTROSTATIC CHARGE ONTO THE XEROGRAPHIC PLATE; A SOURCE OF ALTERNATING CURRENT; A HIGH VOLTAGE DIRECT CURRENT SUPPLY ELECTRICALLY CONNECTED TO SAID SOURCE AND BEING ELECTRICALLY COUPLED TO SAID CORONA DISCHARGE WIRE FOR CHARGING THE SAME; A CONTROL TUBE HAVING A CATHODE ELECTRICALLY CONNECTED TO GROUND, AN ANODE AND A GRID, A RELAY ELECTRICALLY CONNECTED IN SERIES WITH SAID ANODE AND BEING ENERGIZABLE DURING CONDUCTION OF SAID TUBE; SAID RELAY INCLUDING A NORMALLY CLOSED CONTACT SWITCH INTERPOSED BETWEEN SAID DIRECT CURRENT SUPPLY AND SAID SOURCE; A CAPACITOR ELECTRICALLY CONNECTED BETWEEN THE XEROGRAPHIC PLATE AND SAID CATHODE AND BEING ELECTRICALLY COUPLED TO THE GRID OF SAID CONTROL TUBE FOR IMPOSING A BIAS ON SAID GRID IN ACCORDANCE WITH THE CHARGING CURRENT THROUGH THE XEROGRAPHIC PLATE, SAID CAPACITOR HAVING A CAPACITANCE WHEREBY A VARIATION IN THE CHARGING CURRENT ABOVE A PREDETERMINED VALUE WILL VARY THE GRID BIAS TO INITIATE CONDUCTION OF SAID TUBE FOR ENERGIZING SAID RELAY THEREBY OPENING THE CIRCUIT BETWEEN THE SOURCE AND THE DISCHARGE WIRE.

Claim 2

AN APPARATUS FOR CHARGING A XEROGRAPHIC PLATE INCLUDING A CORONA GENERATING DEVICE HAVING AT LEAST ONE CORONA DISCHARGE WIRE POSITIONED ADJACENT TO A XEROGRAPHIC PLATE TO IMPOSE AN ELECTROSTATIC CHARGE ONTO THE XEROGRAPHIC PLATE; A SOURCE OF ALTERNATING CURRENT; A HIGH VOLTAGE DIRECT CURRENT SUPPLY ELECTRICALLY CONNECTED TO SAID SOURCE AND BEING ELECTRICALLY COUPLED TO SAID CORONA DISCHARGE WIRE FOR CHARGING THE SAME; A CONTROL TUBE HAVING A CATHODE ELECTRICALLY CONNECTED TO GROUND, AN ANODE AND A GRID, A RELAY ELECTRICALLY CONNECTED IN SERIES WITH SAID ANODE AND BEING ENERGIZABLE DURING CONDUCTION OF SAID TUBE; SAID RELAY INCLUDING A NORMALLY CLOSED CONTACT SWITCH INTERPOSED BETWEEN SAID DIRECT CURRENT SUPPLY AND SAID SOURCE; A CAPACITOR ELECTRICALLY CONNECTED BETWEEN THE XEROGRAPHIC PLATE AND SAID CATHODE AND BEING ELECTRICALLY COUPLED TO THE GRID OF SAID CONTROL TUBE FOR IMPOSING A BIAS ON SAID GRID IN ACCORDANCE WITH THE CHARGING CURRENT THROUGH THE XEROGRAPHIC PLATE, SAID CAPACITOR HAVING A CAPACITANCE WHEREBY A VARIATION IN THE CHARGING CURRENT ABOVE A PREDETERMINED VALUE WILL VARY THE GRID BIAS TO INITIATE CONDUCTION OF SAID TUBE FOR ENERGIZING SAID RELAY THEREBY OPENING THE CIRCUIT BETWEEN THE SOURCE AND THE DISCHARGE WIRE.