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ELECTROSTATIC DRYER FOR INK JET PRINTERS

IP.com Disclosure Number: IPCOM000024935D
Original Publication Date: 1982-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 156K

Publishing Venue

Xerox Disclosure Journal

Abstract

Ink jet printers can encounter a problem in copy throughput due to the unusually high energy input needed to dry a water-based ink. Certain specifications of printing rates demand that copies be processed every half second, or so. It has been shown that at this rate at least 3000 watts of heat are needed to evaporate the water from a completely darkened page of 8.5 inch-wide paper. Because of inefficiencies, this figure may be larger in practice.

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KEROX DISCLOSURE JOURNAL

ELECTROSTATIC DRYER FOR INK JET PRINTERS
Gilbert M. Elchinger

Proposed Classification US. Cl. 346/75
Int. Cl. Gold 15/8

INK

FIG. I

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FIG. 2

Volume 7 Number 6 November/December 1982 373

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ELECTROSTATIC DRYER FOR INK JET PRINTERS (Cont'd)

Ink jet printers can encounter a problem in copy throughput due to the unusually high energy input needed to dry a water-based ink. Certain specifications of printing rates demand that copies be processed every half second, or so. It has been shown that at this rate at least 3000 watts of heat are needed to evaporate the water from a completely darkened page of 8.5 inch-wide paper. Because of inefficiencies, this figure may be larger in practice.

Several drying techniques have been proposed to solve this problem. These techniques are divided into two general catagories; those which are aimed at evaporating the water as a next step after printing, and those which avoid evaporation as a step. Prior art techniques which have been tried used hot air convection, a hot roll, and/or radiant heat to dry the paper. These techniques may not be effective enough.

The present proposal describes a technique which uses an externally applied oscillating electric field to enhance the evaporation rate of water from the printed ink. The effect of this technique is to reduce the drying time using a conventional heated air blower.

Experiments have confirmed that the evaporation rate from a freely falling drop of water in air is significantly enhanced in the presence of a static electric field (reference: E. D."Blum, et- al; Heat and Mass Transfer in Electromagnetic Fields; Znanive Press, Rina, 1967). G.

                    Kokin an Popov (reference: A. S. Kokin and B. Popo;; "Effect ofVElectrostatic Field on -the Rate of Evaporation of a Charged Particle"; Fluid Mechanics-Soviet Research; Volume 4 Number 6 November 1975) give experimental results for the evaporation rate versus electric field (at various Reynolds numbers, representing different air flow configurations and rates across the drops) which indicate that the evaporation rate increases with electric field and can be more than a factor of two larger than the zero field rate when a 6300 volt/cm electric field is applied. The evaporation rate increases linearly with Reynolds number because of the increasing efficiency of turbulent heat conduction from the drop.

Kokin and Popov have determined that two mechanisms are primarily responsible for electric field enhanced evaporation. First, the electric field increases the surface charge density on the conductive liquid. This increased charge density, elevated by any charge already on the liquid, stretches the surface and reduces surface tension. This reduced surface tension allows greater mass transfer or evaporation...