A feed tray (22) for guiding tribo electrified plastic pieces (2) to a drum
electrode (6) is provided with a vibrator (23), thereby making it possible
to vibrate the plastic pieces (2) to form a thin uniform layer, and to
reliably apply appropriate image force and centrifugal force to the
plastic pieces (2) fed to the drum electrode (6); thus, the plastic pieces
(2) can be separated according to kind with high precision.
