PRINTER DESCRIPTION
6--18 27080 Issue 1 September 98
Feedcircuit. Inkfromthereservoirissuppliedtothecircuitbythehigh
pressurepump. Theinkispumpedthrougha5micronfilter,ajetpump
andthenthrougha69mbar(1psi)PressureReliefValve(PRV)andback
into the reservoir. Thiscircuit providesthe different levels of pressure
to operate the otherink circuits. The electronics system checks the ink
temperature using a sensor encapsulated into part of the 1psi PRV.
Thejetpumpprovidesarestrictionforthemainpumptoworkagainst,
andasaresultofthefluidflowthroughit,createsavacuuminthebleed
line.
Pumppressureismeasuredbythepressuretransducermountedonthe
ink management block which is read, and controlled, by the software.
Ink at pump pressure is fed through a solenoid valve and a 10 micron
filter into the drop generator in the print head. This ink is forced out
ofthe nozzletoformtheinkjet. Nominalinkpressureattheprinthead
is 2900mbar (42psi), or 4000mbar (60 psi) for Pinpoint.
An over--pressure PRV is incorporated and set to operate at 100psi in
case of over pressure in the feed circuit.
Gutter circuit. Non--printed drops of ink from the inkjet are collected
inthe gutter. Thisunusedinkisdrawn fromthe gutter through a filter
bythe vacuumsideofthepumpandreturnedto theink reservoir. The
gutter circuit operates continuously from start--up to shut--down. The
vacuum pump head is kept primed by a small supply of ink from the
pressure side of the pump.
Bleed circuit. A second connection at the drop generator passes ink
throughthebleedsolenoidvalvebacktothereservoirviathejetpump.
Opening the bleed solenoidvalve increasesink flow through the drop
generator and the inherent turbulence clears out any traces of air or
solidmaterial. Thebleedfunctionisusedautomaticallyatstart--upand
at shut--down. It can also be controlled manually for maintenance
purposes.
Viscosity control. Periodic measurements of ink viscosity are taken
automatically. Ink at 69mbar(1psi)istaken fromthe junction between
the 1psi PRV and the jet pump, through a solenoid valve to the
viscometer. The output side of the viscometeris connected to pass ink
back to the reservoir. The viscometer itself consists of a ball in an
inclined tube. Ink flowing through the tube forces the ball to the top,
when the solenoid valve shuts off the ink flow, the ball falls back
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