Canon LBP1760P Service Manual page 104

CHAPTER 2
The upper separation roller is driven via the torque limiter.
Normally, the upper separation roller is imparted with a rotational force in the same direc-
tion as that of the pick-up roller and the lower separation roller (white arrow in the top figure in
Figure 2-8-5). However, since the upper separation roller, envelope and lower separation roller
contact one another, the upper separation roller rotates with the lower separation roller by
transmission of its rotational force via the transported envelope (arrow in the middle figure in
Figure 2-8-5).
On the other hand, if multiple envelopes are picked up, the low friction force between the
envelopes results in a weak rotational force being transmitted to the upper separation roller from
the lower separation roller. Consequently, the upper separation roller rotates in the direction of
its own rotational force, which is the opposite direction of the feeding direction (white arrow in
the bottom figure in Figure 2-8-5), and separates the extra envelope.
By this, the multi-fed envelope is returned to the envelope feeder and is not fed to the print-
er.
Normal
Multiple-feed
The envelope feeder has function to detect multiple envelopes feed by sensing the up and down
motion of the upper feed roller.
If the multiple envelopes are fed between upper and lower feed rollers, and the upper feed
roller is lifted about 0.7mm (equal the thickness of four envelopes), the multiple envelopes feed
sensor (PS902) detects the rise of the upper feed roller.
The envelope feeder driver detects the multiple envelopes feed with the PS902 and notifies the
jam to the engine controller.
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Envelope
Upper separation roller
Lower separation roller
Upper separation roller
Lower separation roller
Upper separation roller
Lower separation roller
Figure 2-8-5
Pick-up roller
Envelope
Pick-up roller
Envelope
Pick-up roller