Epson FX-880 - Impact Printer, Service Manual

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FX-880 Service Manual
Chapter
2 Operating Principles
Rev. A
2-2
2.2 PRINTER MECHANISM
This printer mechanism consists of Printhead, Paper feed mechanism, Carriage movement
mechanism, Tractor feed mechanism, Platen gap adjustment mechanism, Ribbon feed
mechanism, PF motor, CR motor, detectors, and so on.
2.2.1 Printhead
The printhead prints data from the control board on paper using the ink ribbon. The printhead is
mounted on the carriage unit.
2.2.2 Paper Feed Mechanism
The paper feed mechanism picks up paper and transports it to the printhead, then ejects it step by
step or continuously driven by the PF motor. PF motor drives the paper feed mechanism gears
and the platen roller. The top of form and paper out condition are detected by front and rear PE
detector, respectively.
2.2.3 Carriage Movement Mechanism
The carriage movement mechanism carries the carriage unit left and right along the CR guide
shaft and mechanism frame and stops it at any position for printing. It is driven by the torque sent
from the CR motor via the timing belt. Home position is detected by the HP (home position)
detector at power on and CR motor phase changing timing.
2.2.4 Tractor Feed Mechanism
The tractor feed mechanism feeds continuous paper to the printhead and ejects it. The torque
from the PF motor is transferred to the tractor unit via the release mechanism in the paper feed
mechanism. The release mechanism switches the PF motor torque between cut sheet feeding and
continuous paper feeding by the release lever. This printer is equipped with several tractor feeding
methods (front / rear push tractor feeding, front / rear push & pull tractor feeding and front / rear
pull tractor feeding), which is selected according to the tractor unit setting positions and the lever
positions. The tractor detector detects the release lever setting position in cut sheet feeding or
continuous paper feeding.
2.2.5 Platen Gap Adjustment Mechanism
The platen gap (the gap between the platen and the printhead) adjustment mechanism consists of
CR guide shaft, parallelism adjustment bushing, PG adjust lever and PG detector. PG adjust lever
is attached to the left side of the CR guide shaft. The bushings are attached to the both sides of
the frame. As the both sides part of CR guide shaft is eccentric toward external form of it,
printhead approaches or recedes from the platen roller to turn the PG lever forward or backward.
PG detector detects PG lever position. If the lever is set 2nd and more position, the printer gets
into copy mode.
2.2.6 Ribbon Feed Mechanism
The CR motor drives the ribbon feed mechanism via the timing belt. The ribbon feed mechanism
has the sun and planetary gear system. No matter the carriage unit is driven left and right, the ink
ribbon is driven in one direction.