Auto bias control apparatus

Claim 2

In an electrographic apparatus having a development station with a development electrode from which electrostatically attractable toner particles are applied to a movable surface carrying an electrostatic charge pattern to form a toner image on the surface in accordance with such pattern, an improved auto bias control apparatus for applying a development bias signal to said development electrode comprising: a. means disposed a predetermined distance spaced upstream from said development station for sensing the field strength of longitudinal increments of a charge pattern to provide analog signals representative thereof; b. an analog to digital converter responsive to said analog signals to produce digital signals representative thereof; c. means for sequentially storing said digital signals at particular storage locations respectively; and d. bias signal applying means coupled to said storage means and responsive to the digital signals at particular storage locations which correspond to the longitudinal increment of the charge pattern entering the development station for applying development bias signals to said development electrode in increments corresponding to those previously sequentially stored in said storage measns.

Claim 3

The invention as set forth in claim 1 wherein said development station includes at least one magnetic brush.

Claim 4

The invention as set forth in claim 2 wherein said storage means is a digital computer.

Claim 5

The invention as set forth in claim 3 wherein said bias signal applying means includes a digital to analog converter.

Claim 6

For use in electrographic apparatus having a photoconductive web member movable along a predetermined endless path and adapted to have electrostatic images formed thereon at predetermined image areas, and a development station having a development electrode adapted to contact such electrostatic images with a mixture of toner and carrier components to form toner images corresponding to the electrostatic images responsive, the web having a plurality of indicias spaced at predetermined locations thereon, an improved auto bias apparatus comprising: a. means for sensing the electrostatic field strength associated with electrostatic charged patterns of increments of image areas a predetermined distance along the path spaced upstream from said development station to produce analog signals the magnitude of which is representative of the charge on such increments of the image areas respectively; b. means for sensing the indicia to provide a plurality of clock pulse signals; c. an analog to digital converter effective when actuated to be responsive to said analog signals to produce digital signals representative thereof; d. digital to analog converter means coupled to said development station electrode for producing development bias signals and apply same to said development electrode; and e. a digital computer responsive to said clock pulse signals for actuating said analog to digital converter to receive and store converted digital signals in particular storage locations, and apply stored signals from particular storage locations to said digital to analog converter so that the development bias signal applied to said development electrode corresponds at any given time to the increment of the image area at the development station. >

Claim 7

For use in electrographic apparatus having a photoconductive web member movable along a predetermined endless path and adapted to have electrostatic images formed thereon at predetermined image areas, and a development station having a development electrode adapted to contact such electrostatic images with a mixture of toner and carrier components to form toner images corresponding to the electrostatic images responsive, the web having a plurality of indicias spaced at predetermined locations thereon, an improved auto bias apparatus comprising: a. means for sensing the electrostatic field strength associated with electrostatic charged patterns of increments of image areas a predetermined distance along the path spaced upstream from said development station to produce analog signals the magnitude of which is representative of the charge on such increments of the image areas respectively; b. means for sensing the indicia to provide a plurality of clock pulse signals; c. an analog to digital converter effective when actuated to be responsive to said analog signals to produce digital signals representative thereof; d. digital to analog converter means coupled to said development station electrode for producing development bias signals and apply same to said development electrode; and e. a digital computer responsive to said clock pulse signals for actuating said analog to digital converter to receive and store converted digital signals in particular storage locations, and apply stored signals from particular storage locations to said digital to analog converter so that the development bias signal applied to said development electrode corresponds at any given time to the increment of the image area at the development station. >