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OPERATING PRINCIPLES
2.1.4 Paper Feed Mechanism
Figures 2-7, 2-8, and 2-9 show the paper feed mechanism. After the printer loads the paper, it is fed by the
tension roller, platen roller, and front or rear tractor assembly.
The PF motor rotates the tension roller and tractor select gear (Figures 2-8 and 2-9) and moves either the
front or rear tractor assembly. The rotation of the paper feed transmission gear rotates the tractor select gear,
which can engage either tractor train. The tractor select mechanism alternates the engagement of the rear
tractor assembly gear train and front tractor assembly gear train. (Refer to Section 2.1.5 Ribbon Feed and
Tractor Select Mechanisms.)
The front and rear PE sensors are incorporated in the tractor sprocket. When paper is loaded, the paper
pushes the leaf spring and blocks the photo interrupter. When no paper is loaded, the photo interrupter is not
blocked. The top PE sensor is attached to the upper paper guide and is used with the reflection plate on the
paper bail assembly. When paper is loaded, the paper surface reflects the beam; when there is no paper, the
beam is absorbed (not reflected). The Pull tractor sensor monitors whether the pull tractor is installed.
Pull Tractor Sensor
Top PE Sensor
Tension Roller
Paper Bail Lever
TIMING BELT, PF
Tractor Select Gear
Transmission Gear
Pinion Gear
Figure 2-7. Tension Roller and PF Roller Operation
Rev. A
2-7