THEORY OF OPERATION Chapter 2
2 - 3
• Syringe is Present Mode
When the syringe plunger is properly installed in the Mechanical Drive Assembly, the Lever
Pin is in the straight portion of the slot on the Slide, the Drive Potentiometer will be
activated by the middle spring of the Wiper Spring, and the pump will properly detect the
presence of the syringe plunger. The Lever rotates in a manner causing the Lever’s Wiper
Support cams to position the middle spring of the Wiper Spring to make contact with and
compress the two Drive Potentiometer layers together. Under these conditions, the Drive
Potentiometer activates and the pump properly detects the presence of the syringe
plunger.
• Syringe is Not Present Mode
When the syringe plunger is not installed in the Mechanical Drive Assembly, the Drive
Potentiometer will not be activated by the middle spring of the Wiper Spring, the pump will
detect that a syringe is not present, and an alarm will sound if an infusion is attempted.
• Timing
The timing for detection or non-detection of a syringe is fairly complex and thus requires
precise parts. The total movement of the Wiper Spring from the state of no syringe
present to syringe present is only .055 inch. Of the .055 inch movement, approximately
.015 - .020 inches is required to compress the middle spring of the Wiper Spring sufficiently
to generate enough spring force to cause the Drive Potentiometer top and bottom layer to
come into contact causing activation of the Drive Potentiometer. The outer two springs of
the Wiper Spring are for retracting the Wiper Support/Wiper Spring away from the Soft
Potentiometer when a syringe plunger is not installed in the pump or is improperly installed
in the pump.
2.1.1.5 Plunger Driver Assembly
The Plunger Driver Assembly holds and drives the syringe plunger. This assembly
consists of the Upper Plunger Assembly, the Lower Plunger Assembly, and the Drive
Actuator Assembly (refer to Syringe Recognition Sensor). The Lever Pin (see Syringe
Installation and Syringe Recognition Sensor) secures the Upper Plunger Assembly to the
Lower Plunger Assembly.
• Upper Plunger Assembly
The Plunger Driver Slide, used for capturing the syringe plunger, has two Finger Grips on it
which the operator can easily grasp. One end of the Constant Force Spring is attached to
the Upper Plunger Face by a Header Pin press fit to the Face. The opposite end of the
Constant Force Spring is attached to the Spool which has a Stepped Pin going through it.
The ends of the stepped Pin are inserted into holes on the Plunger Driver Slide. As the
Slide is pulled opened or allowed to close, the Constant Force Spring spirals on or off the
Spool and the Slide traverses against the Plunger Driver Carriage found on the Lower
Plunger Assembly.
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