Two-wire corona discharge system for single-step electrostatic image formation

Claim 1

APPARATUS FOR ELECTROSTATICALLY CHARGING A XEROGRAPHIC PLATE IN ACCORDANCE WITH AN OPTICAL IMAGE, INCLUDING: (A) TWO SUBSTANTIALLY PARALLEL CORONA DISCHARGE ELECTRODES POSITIONED SUBSTANTIALLY PARALLEL TO AND IN CHARGING RELATION WITH A XEROGRAPHIC PLATE, THE DISTANCE BETWEEN SAID ELECTRODES AND SAID PLATE BEING FROM ABOUT 0.81 TO ABOUT 1.05 TIMES THE DISTANCE BETWEEN SAID ELECTRODES; (B) ELECTRICALLY CONDUCTIVE SHIELDING MEANS FOR SAID ELECTRODES ADJACENT SAID ELECTRODES AND SUBSTANTIALLY PARALLEL THERETO; (C) A HIGH VOLTAGE ALTERNATING CURRENT POWER SOURCE FOR RAISING SAID ELECTRODES TO CORONA DISCHARGE POTENTIAL; (D) CONTROL MEANS INCLUDING MEANS TO APPLY A PREDETERMINED DIRECT CURRENT POTENTIAL TO SAID POWER SOURCE; (E) PROJECTOR MEANS POSITIONED TO FOCUS AN OPTICAL IMAGE SUBSTANTIALLY UNOBSTRUCTED BY SAID ELECTRODES AND SAID SHIELDING MEANS ONTO THE XEROGRAPHIC PLATE; AND (F) MEANS TO ENERGIZE SAID ALTERNATING CURRENT POWER SOURCE WHILE SAID OPTICAL IMAGE IS FOCUSED ONTO SAID SURFACE.