Corona producing method and apparatus

Abstract

A method and apparatus for producing a uniform elongate corona is provided. The apparatus includes at least one stationary corona electrode coupled to a supply of corona voltage. A moving ground electrode having a series of equally-spaced grounding points is coupled to a bias circuit that returns to ground. The moving ground electrode may be arranged to form a helix on a motor-driven insulating rod, with the longitudinal axis of the rod parallel to the stationary elongate corona electrode at a predetermined distance therefrom. The supply of corona power provides a high negative D.C. voltage or a series of high frequency negative high voltage pulses. The preferred bias circuits include one of a self-bias provided by a high resistance; a high frequency pulsating D.C. power supply circuit; or a fixed value negative D.C. power supply circuit. The moving ground electrode may also embody a moving endless belt having rectangular openings that serve to form a ladder having crossbars of uniform size and spacing within the endless belt, with the crossbars extending perpendicular to the stationary corona electrode and defining the grounding points. The method includes the steps of applying a source of corona power to at least one stationary elongate corona electrode, and moving an elongate ground electrode having a series of equally-spaced grounding points such that the grounding points move along an axis defined parallel to the stationary corona electrode, thereby effecting a substantially uniform corona discharge along the length of the stationary corona electrode.

Dependencies are inferred from the claim text.