14 1260 Infinity Binary Pump User Manual
1 Introduction to the Binary Pump
Overview of the Hydraulic Path
A servo- controlled variable reluctance motor drives the two ball- screw
drives in opposite directions. The gears for the ball- screw drives have
different circumferences (ratio 2:1) allowing the first piston to move at
double the speed of the second piston. The solvent enters the pump heads
close to the bottom limit and leaves it at its top. The outer diameter of
the piston is smaller than the inner diameter of the pump- head chamber
allowing the solvent to fill the gap in between. The first piston has a
stroke volume in the range of 20 µL to 100 µL depending on the flow
rate. The microprocessor controls all flow rates in a range of 1 µL/min to
5 mL/min. The inlet of the first pumping unit is connected to the active
inlet valve which is processor- controlled opened or closed allowing solvent
to be drawn into the first pump unit.
The outlet of the first pump chamber is connected by a 500 µL absorber
capillary to the second pump chamber. The outlets of the second chambers
of both pump channels joined via a small mixing chamber. A coiled
restriction capillary connects the mixing chamber via a pressure pulse
damper, a mixer and a pressure sensor to the purge valve assembly. The
outlet of the purge valve assembly is then connected to the attached
chromatographic system.
When turned on, the pump runs through an initialization procedure to
determine the upper dead center of the first piston of both pump
channels. The first piston moves slowly upwards to the mechanical stop of
the pump head and from there it moves back a predetermined path
length. The controller stores this piston position in memory. After this
initialization the pump starts operation with the set parameters for the
two pump channels.
The active inlet valve is opened and the down moving piston draws
solvent into the first pump head. At the same time the second piston is
moving upwards delivering into the system. After a controller defined
stroke length (depending on the flow rate) the drive motors are stopped
and the active inlet valve is closed. The motor direction is reversed and
moves the first piston up until it reaches the stored upper limit and at the
same time moving the second piston downwards.
Then the sequence starts again moving the pistons up and down between
the two limits. During the delivery stroke of the first piston the solvent in
the pump head is pressed through the outlet valve into the second
pumping unit. The second piston draws in half of the volume displaced by
the first piston and the remaining half volume is directly delivered into
the system. During the drawing stroke of the first piston, the second
piston delivers the drawn volume into the system.
For pump specifications, see “Performance Specifications” on page 26.
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