Ricoh FT7770 Service Manual page 119

FFR Operation
3.
To correctly feed a single sheet of paper, this copier uses an FFR (Feed
and Friction Roller) paper feed system consisting of three sets of rollers:
the pick-up rollers, the feed roller, and the friction rollers.
The pick-up rollers drive the paper to the feed and friction rollers; then,
the feed roller takes over and feeds the paper to the vertical transport
unit. The friction rollers, which cannot turn counterclockwise, allow only a
single sheet of paper to pass through.
The FFR system ensures that only a single sheet of paper is fed. The pick-
up rollers sometimes extract more than one sheet of paper. When this hap-
pens, the extra sheets are stripped from the top sheet by the friction rol-
lers.
The coefficient of friction between the feed roller and the
greater than that between the friction rollers and the paper (F2).
the coefficient of friction (F2) is greater than that between sheets
versely,
of paper (F3). Therefore, the top sheet slides past the friction rollers while
any lower ones are detained.
2-63
30
April, '89
paper (Fl) is
-
c o n