Electric field adjustment for magnetic brushes

Claim 3

The invention as set forth in claim 1 wherein the frequency of the A.C. voltage signal is adjusted to a frequency less than about 4KH z .

Claim 4

In a magnetic brush apparatus for developing electrostatic images on a surface of an image-bearing member by using a developer comprising a mixture of toner and carrier particles that can be triboelectrically charged, said apparatus including a developer applicator having a mixture of toner and carrier particles thereon, magnetic field producing means for forming bristles of such developer on said applicator, means for maintaining contact between the surface of the image-bearing member and such bristles to develop electrostatic images, the improvement comprising: bias means for applying an electric field between the applicator and the image-bearing member, the bias means comprising a steady state component which is selected to minimize background development and a time-varying component having a frequency selected to minimize flaming, and said bias means including means for adjusting the peak-to-peak amplitude of the time-varying component to provide solid image areas that are fully developed and free of flaming but without mottle.

Claim 5

In a magnetic brush apparatus for developing electrostatic images on a surface of an image-bearing member by using a developer comprising a mixture of toner and carrier particles that can be triboelectrically charged, said apparatus including a developer applicator having a mixture of toner and carrier particles thereon, magnetic field producing means for forming bristles of such developer on said applicator, means for maintaining contact between the surface of the image-bearing member and such bristles to develop electrostatic images, the improvement comprising: bias means for applying an electric field between the applicator and the image-bearing member, the bias means comprising a steady state component which is selected to minimize background development and a time-varying component having a frequency selected to minimize flaming, and said bias means including means for adjusting the peak-to-peak amplitude of the time-varying component to provide solid image areas that are fully developed and free of flaming but without mottle.

Claim 6

In a magnetic brush apparatus for applying toner to a member carrying an electrostatic image on a surface of the member by contacting the surface with a developer having a magnetic component and a toner component that can be triboelectrically charged, the improvement comprising: (a) a hollow, non-magnetic, conductive, rotatable cylindrical applicator having a developer comprising a magnetic carrier component and a toner component thereon; (b) magnetic means located inside said applicator for producing a magnetic field which acts upon said magnetic component and causes said developer to be carried by said applicator; (c) means for pressing the surface of the member lightly against the developer on the applicator; and (d) bias control means for applying between said applicator and the member an electric field having a steady state component selected to minimize background development on said member and a time-varying component, the time varying component having a frequency and a peak-to-peak amplitude that can be adjusted, the frequency being adjusted to minimize flaming and the peak-to-peak amplitude being adjusted to fully develop solid area images without producing mottle.

Claim 7

In a magnetic brush apparatus for applying toner to a member carrying an electrostatic image on a surface of the member by contacting the surface with a developer having a magnetic component and a toner component that can be triboelectrically charged, the improvement comprising: (a) a hollow, non-magnetic, conductive, rotatable cylindrical applicator having a developer comprising a magnetic carrier component and a toner component thereon; (b) magnetic means located inside said applicator for producing a magnetic field which acts upon said magnetic component and causes said developer to be carried by said applicator; (c) means for pressing the surface of the member lightly against the developer on the applicator; and (d) bias control means for applying between said applicator and the member an electric field having a steady state component selected to minimize background development on said member and a time-varying component, the time varying component having a frequency and a peak-to-peak amplitude that can be adjusted, the frequency being adjusted to minimize flaming and the peak-to-peak amplitude being adjusted to fully develop solid area images without producing mottle.