Browse Prior Art Database

IMPROVED BEAD PICKOFF ARRANGEMENT

IP.com Disclosure Number: IPCOM000025868D
Original Publication Date: 1988-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 6 page(s) / 295K

Publishing Venue

Xerox Disclosure Journal

Abstract

In electrophotographic applications such as xerography, the developing material commonly used in systems for developing latent images on a charge retentive surface typically comprises a mixture of toner and a "carrier" of larger granular beads of a ferrous material. Toner is attracted to the latent image from the carrier beads to form the toner image. In this type of copier, some carrier beads inevitably adhere to the charge retentive surface after the image is developed. These adhering carrier beads prevent intimate contact between the substrate and toner image during the transfer step. It is thus essential for optimum operation that carrier beads remaining on the charge retentive surface be removed therefrom. The hard carrier beads also have a tendency to abrade and damage the charge retentive surface if not removed prior to reaching the cleaning zone.

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EROX DISCLOSURE JOURNAL

IMPROVED BEAD PICKOFF ARRANGEMENT
Gary L. Whittaker
Daniel M. Bray

103

Proposed Classification

U.S. C1.355/15 Int. C1. G03g 21/00

FIG. 1

Volume 13 Number 4 July/August 1988

217

[This page contains 1 picture or other non-text object]

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IMPROVED BEAD PICKOFF ARRANGEMENT (Cont'd)

XEROX 218 DISCLOSURE JOURNAL

Volume 13 Number 4 July/August 1988

[This page contains 1 picture or other non-text object]

Page 3 of 6

IMPROVED BEAD PICKOFF ARRANGEMENT (Cont'd)

In electrophotographic applications such as xerography, the developing material commonly used in systems for developing latent images on a charge retentive surface typically comprises a mixture of toner and a "carrier" of larger granular beads of a ferrous material. Toner is attracted to the latent image from the carrier beads to form the toner image. In this type of copier, some carrier beads inevitably adhere to the charge retentive surface after the image is developed. These adhering carrier beads prevent intimate contact between the substrate and toner image during the transfer step. It is thus essential for optimum operation that carrier beads remaining on the charge retentive surface be removed therefrom. The hard carrier beads also have a tendency to abrade and damage the charge retentive surface if not removed prior to reaching the cleaning zone.

Carrier bead removal devices are known, such as for example, U.S. 3,894,513 to Stanley et al. and U.S. 3,834,804 to Bhagat et al., which use a stationary magnet having a cylindrical shell rotating thereabout to remove the ferrous carrier beads from the photoreceptor for deposit in a sump or for return to the developer housing. A primary problem, however, is the need to increase the removal force on the beads without simultaneously increasing the magnetic force holding toner on the shell at the removal or drop off point.

With reference to Figure 1, a bead pickoff device 100 may be advantageously located within the confines of developer housing on the down stream side thereof. Bead pickoff device 100 is generally comprised of a cylindrical shell 102 journaled for rotation about a stationary magnet member 104 in the counterclockwise direction, indicated by arrow 103. The direction of shell rotation is not necessarily opposite to the direction of travel of the photoreceptor. Shell 102 may be spaced about 0.1" from photoreceptor belt 10. Both shell 102 and stationary magnet member 104 extend parallel and across the photoreceptor belt 10, transverse to the direction of travel of photoreceptor belt 10. Shell 102 is a non-magnetic material.

Magnetic member 104 includes a permanent magnet 106, having a generally rectangular cross-section, seated in a ferromagnetic strip or channel 108, having at least first and second sides 110 and 112 disposed at an angle in the range of approximately 70"-110" with respect to each other. Channel 108 may be conveniently stamped from 3/32" or 1/16" cold rolled steel or the like,...