THEORY OF OPERATION Chapter 2
2 - 5
The syringe barrel flange is held against the cradle by the tablock bracket. The tablock
bracket is raised or lowered by the rotation of the pendulum. One end of the pendulum
rides in a slot in the barrel clamp slide. The other end of the pendulum raises the tablock
bracket. The slot in the barrel clamp slide has a dogleg at one end that forces the
pendulum to rotate about the pivot screw. When the slide is extended fully by releasing
the brake, the dogleg forces the pendulum to raise the tablock bracket. When the slide is
pushed in, the tablock bracket is clamped against the flange by the tablock spring
(compression spring).
The barrel clamp switch assembly consists of a membrane switch assembly mounted onto
a printed circuit board. The circuit board is mounted onto the two retaining plates by four
switch adhesive pads and four retaining rings. The membrane switch assembly includes a
membrane potentiometer (softpot) that is used to detect the position of the barrel clamp
slide. The position of the slide in reference to the cradle is a measure of the syringe barrel
diameter (syringe recognition). The actuator support, mounted onto the slide, holds the
Teflon actuator button. The actuator button acts as the potentiometer wiper.
The rubber rocker seal protrudes from the cradle. Beneath the rocker seal lies the plastic
rocker. When the syringe barrel is captured between the cradle and face, the rocker is
pressed against the rocker spring (metal leaf spring). Two barrel sensing membrane
switches, connected in series, are adhered onto the rocker spring. The rocker housing
supports the rocker and the rocker spring.
The flange sensing switch, part of the barrel clamp switch assembly, detects the presence
of the barrel flange. The switch is adhesive mounted onto the tablock bracket and is
actuated by the pendulum. The switch is open when a flange is correctly positioned under
the tablock and closed when there is no flange present.
The ESD torsion spring and ESD contact strip reduce the possibility of damage to the
pump by Electro-Static Discharge (ESD). The torsion spring is located between the
retaining plate and the barrel clamp base. Its axis is coaxial with one of the holes for the
#4-40 barrel clamp mounting screws that connect the barrel clamp to the pump. The
purpose of the torsion spring is to make electrical contact between the retaining plate and
the #4-40 screw. The #4-40 screw is electrically grounded to the interior plating of the
pump housing. The ESD contact strip is a beryllium copper leaf spring that fits between
the retaining plate and the Primary Lever Pivot Screw (#6-32 x 1/4”). This contact strip
electrically connects the primary lever assembly to the retaining plate.
The barrel clamp switches are connected to the I/O board inside the pump through the
zebra strip. The zebra strip is a gold plated electrical connector that fits into a slot in the
pump rear case. The zebra strip makes contact with six gold plated pads on the barrel
clamp switch circuit board.
2.1.3 Pole Clamp Assembly
2.1.3.1 Overview
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