Watson-Marlow APEX10 - Manual (Page 17)

DESCRIPTION
17
4.3 Operation of the pump
The heart of the pumphead consists of a specially
constructed pump hose (A) which lies against the inside
of the pump housing (B). The ends of the hose are
connected to the suction and discharge lines (C). A
bearing-mounted rotor (D) with two facing integral
pressing shoes (E) is in the centre of the pumphead. It
rotates clockwise.
In phase 1 the lower shoe compresses the pump hose
by the rotational movement of the rotor, forcing fluid
through the hose. As soon as the shoe has passed, the
hose recovers to its original shape due to the
mechanical properties of the material and fluid is drawn
into the hose.
In phase 2 fluid is drawn through the hose by the
(continuous) turning motion of the rotor.
In phase 3, the second integral pressing shoe
compresses the pump hose. Due to the continuous
rotating movement of the rotor new fluid is sucked in
and fluid that is previously drawn in is pressed out by
the shoe. When the first shoe leaves the pump hose,
the second shoe has already occluded the pump hose
and fluid is prevented from flowing back. This method of
liquid displacement is known as the "positive
displacement principle".
A B E C D