US 4,286,272 AGranted

Ink jet printer and start up method therefor

AssigneeThe Mead Corporation

InventorCharles J. Schwob

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Abstract

An ink jet printer for depositing ink drops on a print receiving medium includes a print head having a fluid receiving reservoir and including an orifice plate defining a row of orifices through which ink from the reservoir passes to form a row of downward extending fluid filaments. The fluid filaments are stimulated to cause break up of each filament into a jet drop stream. A charge electrode plate is positioned beneath the print head and to one side of the row of fluid filaments. The charge electrode plate includes a plurality of charge electrodes with each of the electrodes being positioned adjacent a respective one of the fluid filaments and spaced therefrom by a predetermined distance. An ink supply inlet supplies ink to the fluid receiving reservoir in a direction substantially perpendicular to the row of orifices and to the fluid filaments. The ink supply inlet is positioned on the same side of the fluid filaments as the charge electrode plate. An ink supply outlet removes ink from the fluid receiving reservoir in a direction substantially perpendicular to the row of orifices and to the fluid filaments. The ink supply outlet is positioned on the side of the fluid filaments opposite the ink supply inlet. A valve arrangement supplies fluid to the reservoir at start up of the printer such that a fluid flow across the row of orifices from the inlet to the outlet produces a velocity component in each of the fluid filaments which deflects the filaments outward from their associated charge electrodes. Outward deflection of the filaments prevents wetting of the charge electrodes at start up of the printer.

Claims12

Dependent claims

An ink jet printer for depositing ink drops on a print receiving medium, comprising:

print head means having a fluid receiving reservoir and including an orifice plate defining a row of orifices through which ink from said reservoir passes to form a row of downward extending fluid filaments,
means for stimulating said fluid filaments to cause each of said fluid filaments to break up into a jet drop stream,
a charge electrode plate positioned beneath said print head means and to one side of said row of fluid filaments, said plate including a plurality of charge electrodes, each of said electrodes positioned adjacent a respective one of said fluid filaments and spaced therefrom by a predetermined distance,
ink supply inlet means for supplying ink to said fluid receiving reservoir in a direction substantially perpendicular to said row of orifices and to said fluid filaments, said ink supply inlet means being positioned on the same side of said fluid filaments as said charge electrode plate,
ink supply outlet means for removing ink from said fluid receiving reservoir in a direction substantially perpendicular to said row of orifices and to said fluid filaments, said ink supply outlet means being positioned on the side of said fluid filaments opposite said ink supply inlet means,
means for selectively applying charging potentials to said plurality of charge electrodes such that drops in said jet drop streams are selectively charged,
means for providing a drop deflection field through which said jet drop streams pass, such that drops in said jet drop streams are separated into catch and print trajectories,
means for catching drops in said catch trajectories while permitting drops in said print trajectories to strike said print receiving medium, and
fluid supply control means for controlling the application of ink to and removal of ink from said fluid reservoir, whereby fluid flow across said row of orifices from said inlet means to said outlet means is provided at start up of said printer to deflect said filaments away from said charge electrodes by a distance greater than said predetermined distance, and whereby said fluid flow across said row of orifices is terminated after start up such that said fluid filaments are thereafter spaced from said electrodes by said predetermined distance, said fluid supply control means including means for providing a sufficient back pressure within said fluid receiving reservoir during flow from said inlet means to said outlet means at start up to produce fluid flow through said orifices and formation of said fluid filaments.

6 more elements

An ink jet printer for printing on a print receiving medium comprising:

print head means defining a fluid reservoir and an orifice, and having a fluid inlet and a fluid outlet communicating with said reservoir, said fluid inlet and said fluid outlet being substantially aligned for fluid flow therebetween past said orifice such that fluid emerging from said orifice as a fluid filament has a velocity component in the direction of fluid flow between said fluid inlet and said fluid outlet,
charge electrode means positioned adjacent said fluid filament on the side thereof closest to said fluid inlet, for selectively charging drops formed from said fluid filament,
means for catching charged drops while permitting uncharged drops to strike said print receiving medium, and
valve means for supplying ink to said fluid reservoir through said fluid inlet and removing ink from said fluid reservoir through said fluid outlet at start up of said printer to produce a fluid flow therebetween such that said fluid filament has a velocity component deflecting said fluid filament away from said charge electrode means, said valve means thereafter terminating said fluid flow past said orifice such that said fluid filament is undeflected, said valve means including means for providing a sufficient back pressure within said fluid reservoir during flow from said fluid inlet to said fluid outlet at start up to produce fluid flow through said orifice and formation of said fluid filament.

1 more element

Dependencies are inferred from the claim text.