How Does The Pump Work - Agilent Technologies InfinityLab LC Series 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 in
between. The first piston has a stroke volume in the range of 20 – 100 µL
depending on the flow rate. The microprocessor controls all flow rates in a range
of 1 µL/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.
Agilent InfinityLab LC Series 1260 Infinity II Isocratic and Quaternary Pumps User Manual 22