Grade Motor Assembly And System; Deck And Roller Assembly - Cardiac Science ST 55 Service Manual

Theory of Operation

Grade Motor Assembly and System

The grade motor drives the grade pinion shaft using a chain and a set of speed reduction
sprockets. The grade pinion shaft in turn drives a set of rack gears, which raise and lower
the front of the treadmill.
A grade potentiometer senses the rack gear movement for the grade system feedback. Limit
switches limit the travel of the rack gears in the event of a potentiometer failure or
incorrect calibration.

Deck and Roller Assembly

The deck and roller assembly provides the running surface for the user. This surface
consists of a movable and flexible walking belt supported by a semi-rigid platform. This
platform is supported by a steel-welded frame.
A poly-V drive belt, coupled through a pulley to the drive motor, drives the front roller.
The front roller uses friction to drive the walking belt. A rear roller, acting as an idler
pulley, tensions the walking belt. Both rollers are mounted to the steel support structure.
70-00298-01 A
3-4
TM 55/65 Treadmill 4.0