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IMPROVED DIRECT ELECTROSTATIC PRINTING PRINTHEAD CLEANING CYCLE

IP.com Disclosure Number: IPCOM000027400D
Original Publication Date: 1996-Oct-31
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 98K

Publishing Venue

Xerox Disclosure Journal

Abstract

Proposed is a cleaning cycle for Direct Electrostatic Printing (DEP) printheads in which toner can be returned to a supply rather than deposited on a sheet of paper. Previously, the DEP printhead cleaning cycle involved the transfer of toner through the printhead with a biased AC voltage applied to the paper shoe. The action of the AC field caused freshly transferred toner to oscillate between the printhead and the paper to sputter accumulated toner away from the printhead. At the end of the cleaning cycle, deposited toner was removed from the paper by turning off the AC voltage and leaving a DC voltage on the paper shoe. The process of depositing cleaning sediment (fresh plus sputtered toner) on the paper is unattractive. An improved method for depositing sediment is desired. By altering the cleaning cycle in a manner to be discussed hereinafter, cleaning sediment is returned to the supply through the printhead, leaving the paper and printhead clean to the unaided eye.

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XEROX DISCLOSURE JOURNAL

IMPROVED DIRECT ELECTROSTATIC Proposed Classification PRINTING PRINTHEAD CLEANING CYCLE
Fred W. Schmidlin
John D. Sotack

U. S. C1. 101/37 Int. C1. B41f 17/00

Proposed is a cleaning cycle for Direct Electrostatic Printing (DEP) printheads in which toner can be returned to a supply rather than deposited on a sheet of paper. Previously, the DEP printhead cleaning cycle involved the transfer of toner through the printhead with a biased AC voltage applied to the paper shoe. The action of the AC field caused freshly transferred toner to oscillate between the printhead and the paper to sputter accumulated toner away from the printhead. At the end of the cleaning cycle, deposited toner was
removed from the paper by turning off the AC voltage and leaving a DC voltage on the paper shoe. The process of depositing cleaning sediment (fresh plus sputtered toner) on the paper is unattractive. An improved method for depositing sediment is desired. By altering the cleaning cycle in a manner to be discussed hereinafter, cleaning sediment is returned to the supply through the printhead, leaving the paper and printhead clean to the unaided eye.

Assuming a negative toner and a 0.005 inch gap for both the paper-to-printhead and donor roll-to-printhead gaps, the AC voltage applied to the paper shoe during cleaning is:

VMM,~ = -100 - 800 sin (cot),

where the frequency (0/2x) is several kilohertz (kHz) depending on the toner. The AC voltage is applied to the paper shoe for a period of approximately 1 second. During the first 10 to 100psec of the period, an AC voltage:

V*aonor = 30 + 400 sin (cot),

or whatever is standard for normal printing (with the given to...