Ink jet printer and charge decoupling device therefor

In a jet printer including an electrically grounded print head defining a fluid receiving reservoir from which a plurality of jet drop streams issue, fluid supply means for supplying electrically conductive fluid to said reservoir, drop charging means for selectively charging drops in said streams, to positive and negative charge potentials, and a pair of drop ingesting catchers, and means for supplying electrical deflection potentials of opposite polarity to said catchers such that a deflection field is created between said catchers for deflecting charged drops to said catchers to be ingested thereby,

• an improved charge decoupling system for removing accumulated fluid from said catchers and returning said fluid to said fluid supply means while presenting a high impedance electrical path between said catchers and said fluid supply means, comprising:
• a pair of electrically nonconductive charge decoupling container means, each container means defining an upper fluid receiving chamber and a lower drop chamber, each container means further comprising a perforated plate, defining a plurality of perforations, extending horizontally within said container so as to separate said upper and lower chambers, and drop forming means in said lower drop chamber associated with each of said perforations for defining a capillary path extending downward from each of said openings, whereby fluid drops drip from each of said drop forming means, producing a plurality of drop streams in said lower drop chamber,
• vacuum lines connecting each of said catchers to a respective one of said upper fluid receiving chambers of said container means,
• a common manifold connected to the lower chamber of each of said container means and defining a fluid trap in which drops from said container means are intermingled to neutralize charges carried thereby, and
• supply line means connecting said common manifold with said fluid supply means for returning fluid thereto, whereby said catchers are electrically isolated from each other and from said fluid supply means such that said catchers may be maintained at electrical deflection potentials of opposite polarity, while said print head is grounded and electrically conductive fluid is recirculated from said catchers to said print head.

An ink jet printer comprising:

• print head means including a fluid receiving reservoir and an orifice plate communicating therewith, said orifice plate defining a pair of rows of jet orifices,
• fluid supply tank means for supplying electrically conductive ink under pressure to said fluid receiving reservoir to produce a pair of rows of jet drop streams emanating from said orifices,
• drop charging means for selecting charging drops in a first of said jet drop stream rows to an electrical charge level and for selectively charging drops in the other of said jet drop stream rows to an electrical charge level,
• deflection electrode means including a pair of drop catchers positioned on opposite sides of said pair of row of jet drop streams,
• means for supplying electrical deflection potentials to said catchers to produce a deflection field which deflects selectively charged drops in said jet drop streams outwardly to strike said catchers,
• a pair of vacuum lines, each of said vacuum lines connected to an associated one of said catchers for removing ink therefrom,
• a pair of charge decoupling devices, each of said devices connected to an associated one of said vacuum lines and each defining an upper ink receiving chamber and a lower drop chamber, said upper and lower chambers being partitioned by an intermediate perforated plate defining a plurality of perforations, each of said charge decoupling devices further including means defining downwardly extending, drop-forming capillary paths from said perforations into said drop chamber,
• manifold means connected to said lower drop chambers of said charge decoupling devices for receiving ink therefrom, said manifold means defining a fluid trap in which ink from said pair of charge decoupling devices is intermingled, said manifold means connected to said fluid supply tank means for returning ink from said fluid trap to said fluid supply tank means, and
• partial vacuum means for supplying a partial vacuum to said upper chambers tending to draw ink from said catchers thereinto through said vacuum lines, whereby said drop catchers are substantially electrically isolated from the other elements of said printer.