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Browse Prior Art Database

MAGNETIC FIELD COMPENSATION IN TOUCHDOWN GAP VARIATION

IP.com Disclosure Number: IPCOM000022908D
Original Publication Date: 1976-Apr-30
Included in the Prior Art Database: 2004-Mar-27
Document File: 2 page(s) / 214K

Publishing Venue

Xerox Disclosure Journal

Abstract

In spaced touchdown development, a uniform gap is maintained between the photoreceptor surface and the developer donor in order to produce good quality imaged development, Pulse and DC Bias relieve the close tolerance requirement to some ex~ tent. However, where development forces need to be the greatest (i.e., wide gaps) , the forces are actually the smallest.

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XEROX DISCLOSURE JOURNAL

MAGNETIC FIELD COMPENSATION Proposed Classification
IN
TOUCHDOWN GAP VARIATION U.S. Cl, 96/1.5
Osmar A. Ullrich mt. Cl, G03g 5/04

In spaced touchdown development, a uniform gap is maintained
between the photoreceptor surface and the developer donor in
order to produce good quality imaged development, Pulse and
DC Bias relieve the close tolerance requirement to some ex~
tent. However, where development forces need to be the
greatest (i.e., wide gaps) , the forces are actually the
smallest.

This invention pertains to a method for providing uniform
development forces independent of gap spacing. A diverging
magnetic field is established across the gap by permanent
or electric magnets. One pole piece (say north) is situated
as close to the back of the photoreceptor as is practical.
The south pole piece is situated in back of and some distance
from a microfield donor. A magnetic toner is used and the
magnetic field adjusted such that there is a net force on
the toner to move toward the photoreceptor surface. This
force remains constant independent of gap spacing. A DC
bias is applied between photoreceptor and donor to establish
an electric field opposite to the magnetic field. The mag-'
nitude of this field is an inverse function of gap spacing.
Thus as the gap spacing increases, the electric field
decreases, and the net force on the toner particle is toward
the photoreceptor which assists in moving the toner across
the gap to a weaker image field.

Volume 1 Number 4 A...