Toner containment method and apparatus

DETAILED DESCRIPTION In accordance with the present invention, apparatus and methods for reducing toner contamination in electrostatographic reproducing machine are provided.
In accordance with the principal aspect of the present invention the apparatus comprises an imaging member having an imaging surface capable of supporting an electrostatic latent image comprising image portions charged to a first polarity and magnitude, and non-image portions of the same polarity but substantially reduced magnitude than said image portions, at least one housing containing means to perform an operation on said imaging surface involving charged toner particles, the housing having at least an exit portion through which air normally flows from the housing to other portions of the machine, the housing being provided at the exit portion with at least one electrode extending across the width of and spaced from the imaging surface, and a means to apply an electrical bias of a polarity and magnitude selected relative to the charge on the imaging surface to create an electrical field barrier in the exit portion sufficient to repel the charged toner particles in the exiting air back into the principal portion of the housing substantially without restricting the air flow from the exit portion.
In a specific aspect of the present invention the electrode is positioned substantially parallel to the imaging surface.
In a further specific aspect of the present invention, the electrode is placed adjacent the lip of a magnetic brush developer housing but outside the development zone, and a magnetic field producing means which forms a brush-like array of charged toner particles is in brushing contact with the electrostatic latent image on the imaging surface to develop that image.
In still a further aspect of the present invention, the electrode is postitioned across the width of the imaging surface and also adjacent the inboard and outboard ends of the developer housing.
In a further aspect of the present invention, the imaging surface and the magnetic brush move in oppposite directions through the development zone and the electrode is positioned adjacent the imaging surface entrance to the developer housing