Multicolor electrostatic printing

Claim 1

A SYSTEM FOR ELECTROSTATIC PRINTING WITH A POWDER MIXTURE INCLUDING AT LEAST TWO POWDERS HAVING DIFFERENT PHYSICAL PROPERTIES AND HAVING RELATIVELY OPPOSITE POLARITY TRIBOELECTRIC PROPETIRES, SAID SYSTEM COMPRISING MEANS ESTABLISHING A PRINTING STATION INCLUDING A PLURALITY OF SCREENS EACH OF WHICH HAS A CONDUCTIVE REGION THEREIN INCLUDING APERTURES IN A PATTERN DEFINING THE DESIRED FORM OF SAID PRINTING, THE PARTICLES OF POWDER IN SAID POWDER MIXTURE BEING SMALLER THAN THE APERTURES OF SAID SCREEN ELECTRODE MEANS, MEANS FOR MOVING EACH ONE OF SAID PLURALITY OF SCREENS IN SEQUENCE TO A POSITION SPACED OPPOSITE SAID ELECTRODE MEANS TO THEREBY ESTABLISH SAID PRINTING POSITION, MEANS FOR APPLYING SAID POWDER MIXTURE TO SAID SCREEN WHEN IN SAID PRINTING POSITION, A SOURCE OF POTENTIAL, MEANS FOR PREDETERMINING WITH WHAT POLARITY CONNECTION IS MADE FROM SAID SOURCE OF POTENTIAL OF SAID ELECTRODE MEANS AND A SCREEN AT SAID PRINTING POSITION, MEANS FOR PRODUCING A SIGNAL WHEN EACH OF SAID SCREENS REACHES SAID PRINTING POSITION, MEANS FOR APPLYING SAID SIGNAL TO SAID MEANS FOR PREDETERMIING FOR ESTABLISHING A CONNECTION TO SAID ELECTRODE MEANS AND THE SCREEN WHICH IS AT SAID PRINTING POSITION TO ESTABLISH AN ELECTRIC FIELD THEREBETWEEN WITH A RELATIVE POLARITY TO PERMIT ONLY A DESIRED ONE OF SAID POWDERS TO PASS THROUGH THE APERTURE OF SAID SCREEN INTO SAID ELECTRIC FIELD TO BE MOVED THEREBY AWAY FROM SAID SCREEN TOWARD SAID ELECTRODE MEANS.