Image Transfer And Paper Separation; Pre-Transfer Lamp (Ptl) - Ricoh FW870 User Manual

25 July 1996

IMAGE TRANSFER AND PAPER SEPARATION

5. IMAGE TRANSFER AND PAPER
SEPARATION
[E]
[B] [A] [C] [D]
A174D522.wmf

5.1 PRE-TRANSFER LAMP (PTL)

After the latent image is developed but before the image is transferred to the
copy paper, the drum surface is illuminated by the pre-transfer lamp [A]. This
illumination reduces the negative potential on the drum surface. This
prevents toner particles from being re-attracted to the negatively charged
drum during the paper separation process. It also makes image transfer and
paper separation easier.
5.2 IMAGE TRANSFER
The registration rollers [B] feed the copy paper through the transfer entrance
guides to the transfer section. A high negative voltage (about –5.0 kV) is
applied to the transfer corona wire [C], and the corona wire generates
negative ions. These negative ions are applied to the copy paper, and the
negative charge attracts the positively charged toner away from the drum and
onto the paper. In addition, the paper is held against the drum by the positive
counter charge on the drum.
5.3 PAPER SEPARATION
After image transfer, the copy must be separated from the drum. To break
the attraction between the paper and the drum, the separation corona wires
[D] apply an ac corona (5.0 kV) to the reverse side of the paper. The stiffness
and weight of the paper cause it to separate from the drum.
The separation corona has a negative component. This negative component
holds the toner on the paper to prevent it from being reattracted to the drum
during paper separation. The two pick-off pawls [E] ensure that thin paper,
paper with low stiffness, or upward curled paper separates completely from
the drum.
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