Epson FX-870 Service Manual page 125

Principles of Operation
Push-pull Tractor Method
The push-pull tractor method is a combination of the push and pull tractor methods. Two tractors
are used to advance the paper: one at the front paper entrance and the other at the rear paper
entrance. They operate simultaneously to push and pull the paper through the printer mechanism.
Figure 6-8 illustrates push-pull tractor operation when the paper is fed through the rear paper
entrance. Figure 6-9 illustrates push-pull tractor operation when the paper is fed through the front
entrance.
Pull Tractor Gear
Figure 6-8. Push-pull Tractor Operation Using the Rear Paper Entrance
6-10
Paper (Continuous)
Paper Advance
Reduction Gear
Pull Tractor
Push Tractor
Push Tractor Gear
Tractor Reduction Gear
,PF Motor Pinion Gear
Epson FX-870/1170 '