Service manual

28 March 2006 PAPER FEED
6-41
Detailed
Descriptions
again. In this way, the top of the paper stack remains at the same position during
printing.
When the tray lowers, the lower limit position is detected by the lower limit sensor
[F], which is beside the paper table motor.
When paper runs out, the paper feed table lowers, until the paper table lower limit
sensor (not shown) detects the lower limit position.
Why do we have two height sensors?
Note that the feeler [H] is at a different part of the stack from the pick-up roller [D].
Some types of paper have a different stack thickness at different parts of the stack.
This is notably true for envelopes, which have a greater stack thickness at the
leading edge. The pick-up roller contacts the stack a small distance away from the
leading edge, so the stack is a bit thicker than detected by an actuator attached to
the pick-up roller.
Then, if there is only one height sensor, it might detect that the table is at the
correct height at the wrong time, or that the stack height is too low at the wrong
time.
Then a misfeed will occur.
So, having two sensors prevents misfeeds.
Paper End Detection Mechanism
The paper end sensor [G] is under the paper table to detect when the paper on the
table runs out.
Paper Size Detection
NOTE: The paper size is not detected in this model, because there are no paper
size sensors. As a result, the master is always made at full size. (Also,
there is no size sensor for originals.)