How Does The Pump Work - Agilent Technologies 1200 Series Reference Manual

7 Introduction to the Quaternary Pump
Figure 44

How does the Pump Work?

The liquid runs from the solvent reservoir through the degasser to the MCGV
and from there to the active inlet valve. The pump assembly comprises two
substantially identical plunger/chamber units. Both plunger/chamber units
comprise a ball-screw drive and a pump head with one sapphire plunger 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 plunger to move at twice the speed
of the second plunger. The solvent enters the pump head close to the bottom
limit and leaves it at its top. The outer diameter of the plunger is smaller than
the inner diameter of the pump head chamber allowing the solvent to fill the
gap in between. The first plunger has a stroke volume in the range of 20–100 µl
depending on the flow rate. The microprocessor controls all flow rates in a
204
Vacuum chamber (Degasser)
Inlet
valve
Hydraulic Path of the Quaternary Pump
From
solvent
bottles
Damper
To sampling
unit and
column
Outle
tvalv
To waste
1200 Series QP Reference Manual