22 Agilent InfinityLab LC Series 1260 Infinity II Isocratic- and Quaternary Pumps User Manual
1
Introduction
Overview of the Hydraulic Path
How Does the Pump Work?
In the quaternary pump, the liquid runs from the solvent reservoir through the
degasser to the MCGV and from there to the inlet valve.
For the isocratic pump, the solvent bottle is directly connected to the inlet
valve.
The pump assembly comprises two substantially identical piston/chamber
units. Both piston/chamber units comprise a ball-screw drive and a pump
head with one sapphire piston for reciprocating movement in it.
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 twice the speed
of the second piston. The solvent enters the pump head 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 inbetween. The first piston has a stroke volume in the range of 20 – 100 L
depending on the flow rate. The microprocessor controls all flow rates in a
range of 1 L/min – 10 mL/min. The inlet of the first pumping unit is
connected to the inlet valve.
The outlet of the first piston/chamber unit is connected through the outlet
valve and the damping unit to the inlet of the second piston/chamber unit. The
outlet of the purge valve assembly is then connected to the following
chromatographic system.
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