Sheet Feeder Unit Structure - Canon BJC-8500 Service Manual

Part 4: Technical Reference BJC-8500

3.5.2 Sheet feeder unit structure

The printing paper is stacked on the sheet feeder hooked by the claws at the left and
right corners of the sheet feeder. The loading claw is provided for improving the paper
loading performance. The left and loading claw follows sliding movement of the side
guide.
When purge motor drive is transferred to the sheet feeder gear via the sheet feeder
drive gear, the pick-up roller rotates, and the printer starts printing operations.
Printing paper such as plain paper is held by the claws on both sides, picked up one
sheet at a time, and pushed into the paper feed section. When thicker printing paper
such as envelopes are picked up, raise the left and right guides so that the printing
paper is picked up without being hooked by the left and right claws. When photo
glossy papers GP-301 are picked up, raise the left guide only.
The initial position of the pick-up roller is detected by the photo-interrupter pick-up
roller sensor on the carriage board, and is determined by the number of pulses output
from the paper feed motor.
When the paper end sensor detects the printing paper, the number of paper feed
motor (stepping feed) pulses is managed to prevent skew feed, and the printing paper
is automatically fed to the printing start position. If the printing paper is not detected
by the paper end sensor, a paper pick-up error is generated.
During manual feed, the user must insert the printing paper into the manual feed slot
until the paper end sensor detects the printing paper. Also, the printing paper passes
along a pick-up path different to that during automatic pick-up by the sheet feeder.
So, printing paper can be fed manually even if printing paper is stacked in the sheet
feeder.
When the printing paper pushed into the paper feed section is detected by the paper
end sensor within the preset time, paper is picked up from the printing start position.
Left Guide
Side Guide
Pick-up Roller
Right Guide
During Sheet Feeder Drive
Left Claw
Purge Motor
Sheet Feeder Gear
Loading Claw
Right Claw
Figure 4-30 Structure of Sheet Feeder Unit
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