Corona charging apparatus

DETAILED DESCRIPTION In achieving the above and related objects, the invention provides a corona charging device comprising an elongate conductor with a dielectric sheath, and an overlying conductive grid.
The dielectric sheathed conductor and conductive grid are both mounted against an insulating substrate.
This apparatus may be used for corona charging and discharging by means of a varying potential between the elongate conductor and the conductive grid.
The conductive grid is maintained at ground potential for charge neutralization, and at a limiting bias potential for corona charging.
In accordance with one aspect of the invention, the grid electrode comprises a one or two directional array of fine conductive members.
In the preferred embodiment, the grid electrode comprises a fine wire mesh screen.
In an alternative embodiment, the grid comprises a parallel array of fine, closely spaced wires, transverse to the axis of the elongate conductor.
In accordance with another aspect of the invention, the elongate conductor may have a variety of cross sections.
In the preferred embodiment, the elongate conductor comprises a cylindrical wire.
In an alternative embodiment, this electrode comprises an etched foil.
In accordance with a related aspect of the invention a variety of insulating materials, preferably inorganic, may be utilized in the dielectric sheath for the elongate conductor.
In accordance with a further aspect of the invention, the conductive grid and the dielectric sheathed conductor form substantially parallel electrodes.
In accordance with a related aspect, the grid may have a variety of transverse cross sections wherein the grid contacts or is closely spaced from the dielectric sheath at or near its outer surface.
In accordance with an alternative embodiment of the invention, the corona charging apparatus may include a thin dielectric separating the conductive grid from the elongate conductor, but not completely covering the latter member.
In accordance with a further alternative embodiment of the invention, the insulating substrate may include a slot to house the dielectric sheathed conductor