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84 Theory of operation Q2431-90912
Lifter-driver operation
The lifter driver keeps the media stack surface at a specific level in order to have a stabilized
pickup operation regardless of the size of the media in the tray 2 cassette. The DC controller
PCA operates the lifter driver motor (M103) for 50 seconds. The motor stops when the paper
stack position sensor (PS107) detects the media. If the paper stack position sensor does not
detect any media within 8 seconds after the lifting operation has begun, the DC controller PCA
determines there has been a lifter driver motor failure and a message appears on the control-
panel display (see “Alphabetical printer messages” on page 258 or “Numerical printer
messages” on page 274). The DC controller PCA stops the lifting operation if the paper stack
position sensor detects the absence of the tray 2 cassette.
Multiple feed prevention
The printer uses the separation roller in tray 2 to prevent multiple-feeding. Normally, the
separation roller rotates in the same direction as the feed roller. The separation roller is equipped
with a torque limiter, but because the force of the feed roller exceeds that of the torque limiter, the
separation roller is actually driven by the feed roller.
If multiple sheets of media are picked up, however, the low friction force between the sheets
weakens the rotational force from the feed roller to the separation roller. Consequently, the
torque limiter takes control of the separation roller, and rotates the separation roller in the reverse
direction, which removes the extra sheets.
Figure 19. Multiple feed prevention
Pickup roller
Feed roller
Driving force transmitted from the feed roller
Separation roller
Driving force transmitted from the motor through the torque limiter
Normal
Multiple feed
Media