Xerox Corporation

William M Allen

Delmer G Parker

Jerome E May

Howard M Stark

Gerald M Fletcher

James Edward Williams

Richard P Germain

Carrier bead pick-off device including a magnet assembly and an enclosure in which the magnet assembly is reciprocated between a first position where carrier beads are picked off the photoreceptor and a second position where the carrier beads are caused to be returned to a developer housing structure. The enclosure in one embodiment of the invention forms part of the developer housing structure. The magnet is retracted such that it follows the contour of the enclosure so that the carrier beads are swept into the developer housing structure.

Compact magnetic bead pick-off device

A hybrid development system for developing composite tri-level xerographic latent images in which conductive magnetic brush (CMB) development system is employed at the first development station and insulative magnetic brush (IMB) development system is used at the second station. In order to preclude spurious fringe field development by the IMB development system at the second development station the conductivity of the IMB developer is in the order of 10.sup.-13 to 10.sup.-15 ohm-cm. Additionally, a scorotron corona charging device located between the two development housings may be used to charge the image developed at the first station to the same potential as the background (white level) thereby eliminating spurious fringe field development by the IMB developer with a conductivity less than 10.sup.-13 ohm-cm at the second development station.

Hybrid development scheme for trilevel xerography

Balanced, efficient corona transfer for both the charged area image and the discharged area image of a developed tri-level image is obtained by the provision of a selective pre-transfer charge corona device in combination with a pre-transfer discharge lamp. While improved transfer over prior art devices is obtained using a pre-transfer lamp prior to pre-transfer charging the preferred embodiment of the invention utilizes a pre-transfer lamp before and in coincidence with pre-transfer charging.

Selective pre-transfer corona transfer with light treatment for

Tri-Level Highlight color imaging apparatus utilizing two-component developer materials in each of a plurality of developer housings. The triboelectric properties of the toners and carriers forming the two-component developers are such that inter-mixing of the components of each developer with the components in another developer housing is minimized.

Preferred toner/carrier properties

Tri-Level Highlight color imaging apparatus and cleaner apparatus therefor. Improved cleaning of a charge retentive surface is accomplished through matching the triboelectric properties of the positive and negative toners and their associated carriers as well as the carrier used in the magnetic brush cleaner apparatus. The carrier in the cleaner upon interaction with the two toners causes them to charge to the same polarity. The carrier used in the cleaner is identical to the one use in the positive developer. The carrier of the negative developer was chosen so that the toner mixed therewith charged negatively in the developer housing.

Highlight color imaging apparatus

A magnetic brush developer apparatus including a plurality of developer housings each including a plurality of magnetic brush rolls associated therewith. Conductive magnetic brush (CMB) developer is provided in each of the developer housings. The CMB developer is used to develop electronically formed images. The physical properties such as conductivity, toner concentration and toner charge level of the CMB developers are such that density fine lines are satisfactorily developed notwithstanding the presence of relatively high cleaning fields.

A magnetic brush developer apparatus comprising a plurality of developer housings each including a plurality of magnetic rolls associated therewith. The magnetic rolls disposed in a second developer housing are constructed such that the radial component of the magnetic force field produces a magnetically free development zone intermediate a charge retentive surface and the magnetic rolls. The developer is moved through the zone magnetically unconstrained and, therefore, subjects the image developed by the first developer housing to minimal disturbance. Also, the developer is transported from one magnetic roll to the next. This apparatus provides an efficient means for developing the complimentary half of a tri-level latent image while at the same time allowing the already developed first half to pass through the second housing with minimum image disturbance.

Single pass highlight color printer including a scavengeless developer

Printing apparatus for forming toner images in black and at least one highlighting color in a single pass of a change retentive imaging surface through the processing areas, including a development station, of the printing apparatus. The development station includes a pair of developer housings each of which has supported therein a pair of magnetic brush development rolls which are electrically biased to provide electrostatic development and cleaning fields between the charge retentive surface and the developer rolls. The rolls are biased such that the development fields between the first rolls in each housing and the charge retentive surface are greater than those between the charge retentive surface and the second rolls and such that the cleaning fields between the second rolls in each housing and the charge retentive surface are greater than those between the charge retentive surface and the first rolls.

Developer apparatus for a highlight printing apparatus

Undesirable transient development conditions that occur during start-up and shut-down in a tri-level xerographic systemw when the developer biases are either actuated or de-actuated are obviated by using a control strategy that relies on the exposure system to generate a spatial voltage ramp on the photoreceptor during machine start-up and shut-down. Furthermore, the development systems' bias supplies are programmed so that their bias voltages follow the photoreceptor voltage ramp at some predetermined offset voltage. This offset is chosen so that the cleaning field between any development roll and the photoreceptor is always within reasonable limits. As an alternative to synchronizing the exposure and developing characteristics, the charging of the photoreceptor can be varied in accordance with the change of developer bias voltage.

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Webster, NY, United States of America

William M Allen