Development apparatus for continuous rotary electrostatographic apparatus

Claim 1

IN AN XEROGRAPHIC APPARATUS A ROTATABLE DRUM, A PHOTOCONDUCTIVE PERIPHERAL SURFACE FORMED THEREON, DRIVE MEANS FOR ROTATING SAID DRUM, MEANS FORMING CHARGING AND EXPOSING STATIONS ADJACENT SAID DRUM FOR FORMING AN ELECTROSTATIC IMAGE AS A CHARGE PATTERN ON SAID PHOTOCONDUCTIVE SURFACE, AND DEVELOPMENT MEANS ADJACENT SAID DRUM TO FORM A VISIBLE IMAGE CORRESPONDING TO SAID CHARGE PATTERN, SAID DEVELOPMENT MEANS COMPRISING A DEVELOPMENT ELECTRODE HAVING A CURVED SURFACE SPACE IN CLOSELY CONFRONTING RELATION TO SAID PERIPHERAL SURFACE TO MODIFY THE DEVELOPMENT FIELD, THE IMPROVEMENT COMPRISING: CLOSED PASSAGE MEANS FOR INTERPOSING TWO INDEPENDENT LAYERS OF FLUID IN SAID FIELD, MEANS FOR CONDUCTING AIR FROM A SOURCE AT INCREASED PRESSURE INTO SAID PASSAGE MEANS, AND TUBULAR MEANS FOR DISPERSING DEVELOPER POWDER IN A FIRST OF SAID LAYERS, SAID FIRST LAYER BEING INTRODUCED INTO SAID FIELD DOWNSTREAM FROM A SECOND OF SAID LAYERS, SAID SECOND LAYER OPERATING TO PREVENT DEVELOPER POWDER FROM LEAVING SAID FIELD, EACH SAID PASSAGE MEANS FURTHER CHARACTERIZED AS HAVING AN INLET SUBSTANTIALLY SYMMETRICAL IN GEOMETRIC CONFIGURATION, A TRANSITION ZONE GRADUALLY TAPERING DIVERGENTLY IN WIDTH DIMENSION AND CONVERGENTLY IN THICKNESS DIMENSION AND AN OUTLET WHICH IS AT LEAST AS THIN AS AND AT LEAST AS WIDE AS THE DEVELOPMENT ZONE BETWEEN THE PHOTOCONDUCTIVE SURFACE AND THE ELECTRODE AREA, THEREBY TO DEPOSIT THE DEVELOPER POWDER ON THE SURFACE IN THE CONFIGURATION OF THE CHARGE PATTERN AND INSURE LAMINAR FLOW OF THE COMBINED LAYERS THROUGH THE DEVELOPMENT FIELD.