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OUTLOOKTM 200 SERVICE MANUAL
and pressure of the fluid delivered. The various important parts of the bezel
mechanism are the bezel, the inlet valve, the transfer valve, the restriction valve,
the petal module, the refill piston, and the pressure transducer. In the following
paragraphs, the mechanism is described as it is seen from the front of the pump.
The door of the pump limits the movement of the cassette and helps to contain
the pressure required for pressurized fluid delivery. The door must be closed and
securely latched for the pump to operate.
7.2.4.2
Restriction/Outlet Valve
The restriction/outlet valve is the right-most valve which extends through the
bezel. The valve is under servo-control by the pump software and the restriction
motor. The purpose of the valve is to provide the proper downstream resistance
at the selected operating pressure. The restriction yoke has an optical sensor at
the tip, called an optical yoke sensor, giving valve position information to the
pump's system.
7.2.4.3
Petal Module
The function of the petal module is to pressurize the delivery chamber of the
cassette. The petal module is located just to the left of the restriction valve and
has a protective rubber cover. It is pushed forward by the main stepper motor
during fluid delivery and retracts as fluid is pushed into the delivery chamber
from the refill chamber during the refill operation. The pump system obtains
main motor position from the main motor optical encoder.
7.2.4.4
Refill Piston
The refill piston is inversely and mechanically linked to the main motor drive.
This allows the cassette to refill while the petal module is delivering. The refill
piston is the large disc to the left of the petal module. The face of the piston is a
magnet of special construction. It has unusually strong magnetic properties,
which allows the piston to remain attached to the metal disk, part of the refill
chamber of the cassette, even when refilling from a fluid supply positioned
below the inlet of the pump (a negative head height).
7.2.4.5 Transfer and inlet Valves
The transfer valve controls the transfer of fluid from the refill chamber of the
cassette to the delivery chamber and is located between the petal module and the
refill piston. The inlet valve controls the flow of fluid into the refill chamber and
is located to the left of the refill piston. These two valves are mechanically
linked to provide inverse operation and are operated by the pump system via the
transfer solenoid.
Page 62 of 144
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950953 Rev B (9/04)
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