Chapter 2 THEORY OF OPERATION
2 - 4
• Lower Plunger Assembly
The Plunger Driver Lever rotates in the Plunger Driver Carriage on two Lever Screws that
have precise diameters. The Lever Screws act as hubs for the Lever and secure the Lever
to the Carriage. The Lever Pin is pressed into the Lever and Lever rotation is due to the
movement of the pin in the Slide slot as the Slide is moved in and out. Two cams on the
Lever move against two cam surfaces on the Face whenever the Slide is pulled out or
released. As the Slide is pulled all the way out from the pump, the cams meet and push
the Face away from the syringe plunger permitting the syringe to be easily loaded into the
Plunger Driver Assembly.
Two Sleeve Bearings are press fit into the Carriage allowing the Plunger Driver Assembly
to move freely on the Shaft. The Driver Actuator Assembly is designed to move freely in
the Carriage. The Face is also designed to move freely against the Carriage.
The Lockplate is free to move in the V in the Carriage. There are two Compression
Springs that push the Lockplate out of the Carriage to lock the two (left hand and right
hand) Halfnuts shut. Two Retaining Rings secure the Halfnuts to Halfnut Pins that are
press fit into the Carriage. The Halfnut rotates freely on these pins. The Halfnut
Compression Spring pulls the Halfnuts together onto the Leadscrew. When driving a
syringe, the design of the Plunger Driver Assembly causes the Halfnuts to grab onto the
Leadscrew. The Lockplate is required to keep the Halfnuts closed.
2.1.2 Barrel Clamp Assembly
2.1.2.1 Overview
The barrel clamp assembly mounts externally onto the back of the pump case. The
purpose of the barrel clamp is to secure the barrel of the syringe to the pump housing. The
barrel clamp accommodates syringe barrels from three different manufacturers and of
volumes from 1 mL to 60 mL. The “syringe recognition” feature measures the barrel outer
diameter for recognition purposes. In addition, the barrel clamp must detect that the barrel
is securely fastened and that the barrel flange is locked in place.
2.1.2.2 Major Components
The backbone of the barrel clamp is the clamp base. The syringe barrel is captured
between the gray colored cradle and the clear plastic clamp face. The cradle is attached to
the clamp base and the clamp face is attached to the barrel clamp slide. The slide is
spring-loaded and extends outwards from the cradle. The slide is held against the base by
the two retaining plates. The barrel clamp brake locks the slide in place against the force
of the extension spring. The brake can be released by moving the primary release lever.
The braking force is applied by the brake spring (compression spring). The primary
release lever may also be actuated by the secondary lever. The fit of the barrel clamp
brake into the clamp base ensures that the brake releases automatically when the slide is
pushed inwards. Hence, the release levers are only required to open the slide.
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