Ricoh FT6645 Manual page 70

23 April 1993 DEVELOPMENT
4. DEVELOPMENT
4.1 OVERVIEW
[B]
[C]
[D]
[A]
This copier uses a double roller (diameter 20 mm each) development (DRD)
system. This system differs from single roller development systems in that (1)
it develops the image in a narrower area, (2) it develops the image twice, and
(3) the relative speed of each development roller against the drum is
reduced. Also, finer toner (Approx. 9 µm) and developer (Approx. 70 µm) are
used. Both the DRD system and new supplies improve the image quality,
especially of thin horizontal lines, the trailing edges of the half-tone areas,
and black cross points.
The paddle roller [A] picks up developer in its paddles and transports it to the
upper development roller [B]. Internal permanent magnets in the
development rollers attract the developer to the development roller sleeve.
The upper development roller carries the developer past the doctor blade [C].
The doctor blade trims the developer to the desired thickness and creates
backspill to the cross mixing mechanism.
The development rollers continues to turn, carrying the developer to the OPC
drum [D]. When the developer brush contacts the drum surface, the
negatively charged areas of the drum surface attract and hold the positively
charged toner. In this way, the latent image is developed.
The development roller is given a negative bias to prevent the toner form
being attracted to the non-image areas on the drum surface that may have a
slight residual negative charge.
After turning another 100 degrees, the developer is returned to the paddle
roller [A].
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