Corona charge device

Claim 1

A corona charge device comprising a corona discharge wire connected to a high voltage source and a grounded conductive shield electrode including an elongate rectangular closed vessel including side walls and end walls, said vessel being open at its bottom between opposed side walls to define an opening, the corona discharge wire being surrounded by said vessel and being resiliently supported by said end walls of said vessel such that a flow of ions is directed downwardly from said corona discharge wire through said opening toward a field electrode, said device further comprising means for controlling the flow of ions toward said field electrode including elongate insulating plates each having upper and lower half portions, said upper half portions being respectively secured to and extending along each side wall of said conductive shield electrode and said lower half portion being inclined at an angle with respect to said upper half portion to reduce the transverse width of said opening, means for maintaining said insulating plates at an electric potential which is higher than the electric potential of said grounded conductive shield electrode and means for setting an electrical potential of at least the inner surface of said shield electrode to an electrical potential between the electrical potential applied from said high voltage source to said corona discharge wire and ground electrical potential.