Ricoh FT8680 Service Manual page 115

31 July 1995 FUSING
13. FUSING
13.1 OVERVIEW
[C]
[A]
[D]
[C]
[E]
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[B]
[F]
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The image fusing on the copy paper is made by the hot roller [A] and
pressure roller [B]. The hot roller has three heat pipes [C]. These pipes
deliver extra heat from both ends of the hot roller to the center of the roller to
distribute heat evenly along the roller. This is especially effective for small
paper that passes only through the center of the roller. The hot roller has one
internal fusing lamp (1600 W). The lamp turns on during initial warm-up, and
as necessary to keep the hot roller at operating temperature (198°C). The
CPU monitors the hot roller temperature through a thermistor. A thermofuse
(169°C) protects the unit against overheating.
The oil supply roller [D] applies silicon oil to the hot roller directly. Silicon oil is
used for several reasons: it keeps rollers clean by reducing the amount of
toner transferred to them, it reduces adhesion between paper and the hot
roller, and it reduces paper curl. As the toner designed for this machine
includes a substitute for the silicon oil, only a small amount oil is used for
fusing.
The hot roller and pressure roller have stripper pawls [E] to prevent
wrap-around jams.
The pressure roller is cleaned by a steel cleaning roller [F]. Toner adheres to
steel more readily than to silicon rubber.
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