Magnetic brush developing apparatus

Claim 2

In a xerographic development apparatus for developing the latent electrostatic images formed on a uniformly charged photoconductive member, the combination of: developing means for developing said latent electrostatic images on said photoconductive member, said developing means including a developer mix comprised of uncoated conductive carrier and ink particles, and at least one magnetic developing brush, said brush being free of electrical bias to permit use of said uncoated conductive carrier, and means to suppress image background while avoiding biasing of said magnetic brush, said suppressing means comprising a charge producing device upstream of said magnetic developing brush adapted to expose said photoconductive member to a charge opposite in polarity to the charge on said photoconductive member before development whereby to reduce image background charge levels.

Claim 3

The apparatus according to claim 1 including means to ground said magnetic developing brush.

Claim 4

The apparatus according to claim 1 in which said charge producing device is adapted to reverse the polarity of the charge of said image background areas.

Claim 5

In a xerographic development apparatus adapted to use a developer mix incorporating uncoated conductive carrier particles, the combination of: at least one developing member; means to ground said developing member to obviaTe shorting of said developing member by said conductive carrier, and means to suppress the background areas of a latent electrostatic image to enhance development thereof by said developing member without placing a bias voltage on said developing member, said background suppressing means comprising a charge producing device upstream of said developing member adapted to reverse the polarity of the charge comprising said image background areas.

Claim 6

In a xerographic development apparatus adapted to use a developer mix incorporating uncoated conductive carrier particles, the combination of: at least one developing member; means to ground said developing member to obviaTe shorting of said developing member by said conductive carrier, and means to suppress the background areas of a latent electrostatic image to enhance development thereof by said developing member without placing a bias voltage on said developing member, said background suppressing means comprising a charge producing device upstream of said developing member adapted to reverse the polarity of the charge comprising said image background areas.

Claim 7

In an electrostatic reproduction apparatus having a photoconductive member on which latent electrostatic images of the originals being reproduced are made, first charging means for uniformly charging said member in preparation for imaging, means to expose said charged member to a document being copied to form a latent electrostatic image of the document thereon, means to develop the latent image with a developer material consisting of a mixture of bare carrier and toner particles, the developing means including a housing for said mixture and at least one magnetic brush, and transfer means for transferring the image developed on said member to copy substrate material, the combination of: means connecting said magnetic brush to a ground common to said developer housing whereby a bridging circuit established by a conglomeration of said carrier particles between said brush and said housing will not change the developing characteristics of said magnetic brush; and second charging means upstream of said magnetic brush to generate a charge opposite said first charging means, said second charging means charge being adapted to reduce overall latent electrostatic image charge so that the charge comprising image background areas are reversed to suppress developing of said image background areas.

Claim 8

In an electrostatic reproduction apparatus having a photoconductive member on which latent electrostatic images of the originals being reproduced are made, first charging means for uniformly charging said member in preparation for imaging, means to expose said charged member to a document being copied to form a latent electrostatic image of the document thereon, means to develop the latent image with a developer material consisting of a mixture of bare carrier and toner particles, the developing means including a housing for said mixture and at least one magnetic brush, and transfer means for transferring the image developed on said member to copy substrate material, the combination of: means connecting said magnetic brush to a ground common to said developer housing whereby a bridging circuit established by a conglomeration of said carrier particles between said brush and said housing will not change the developing characteristics of said magnetic brush; and second charging means upstream of said magnetic brush to generate a charge opposite said first charging means, said second charging means charge being adapted to reduce overall latent electrostatic image charge so that the charge comprising image background areas are reversed to suppress developing of said image background areas.