Hospira LifeCare XL Series, Technical & Service Manual

Page: 43 / 278

SECTION 4 THEORY OF OPERATION
430-00587-008 (Rev. 2/05) 4 - 18 Plum XL Series
Figure 4-2. Fluid Path in the Cassette
4.3.2
MECHANISM ASSEMBLY
The mechanism assembly is a fully self-contained unit consisting of the motor and valve
assemblies, primary/secondary valve subsystem, inlet/outlet valve subsystem, plunger
drive subsystem, air bubble (ultrasonic) sensor assemblies, cassette door, and pressure
sensor assembly. The motor and valve assemblies, primary/secondary valve subsystem,
inlet/outlet valve subsystem, and plunger drive subsystem are detailed in the following
sections.
During infusion system operation, the mechanism assembly plunger motor drives a lead
screw that is coupled to a nut in the plunger. The motor action and lead screw move the
plunger forward to cause the delivery of approximately 0.33 mL of fluid per cycle. The
plunger motion is synchronized to the valve motors to provide controlled fluid delivery.
04K01002
PRIMARY
PRIMARY VALVE
AIR TRAP CHAMBER
INLET VALVE
OUTLET VALVE
PRESSURE SENSOR
SECONDARY VALVE
AIR-IN-LINE SENSOR (PROXIMAL)
SECONDARY
PUMPING CHAMBER
AIR-IN-LINE SENSOR (DISTAL)
PRECISION GRAVITY
FLOW REGULATOR ( AND SHUT-OFF)