Service manual

3 • Theory Of Operation
3-8 DM300c/DM400c/DM475 Service Manual (SV61801 Rev. D)
Tape Feeder
The tape feed unit has a ca-
pacity of 55 tape strips and can
feed up to 65 strips per minute.
The unit consists of a tape feed
motor and gear train that drives
a feed roller equipped with
a rubber tire. When the user
presses the tape button on the
control panel, the printer trans-
port starts. the tape motor turns
counterclockwise when viewed
as in Figure 3-4A. This drives
the tape roller clockwise, feed-
ing the tape strip under sensor
PS1. The tape is driven into the
nip of the segmented feed roll-
er. Since the tape is not wide
enough to be gripped by the
printer transport belt, it is trans-
ported by the tape transport
roller located just downstream
from the segmented roller and
rubber exit roller located on the
main drive shaft as shown in
Figure 3-4B.
The tape feeder has a pivoting spring-loaded pusher plate containing two
ridges immediately under the roller. The pusher plate presses the first tape
in the stack against the rubber drive roller so that it is fed when the roller
rotates. A single tape is flexible enough to advance through the curved exit
path of the tape feeder and into the printer transport. The two ribs on the
pusher plate keep the remaining tapes in a concave shape perpendicular to
the feed direction. The coefficient of friction between tapes is not sufficient
to drive them around the curved exit path. After the lead edge of a tape is
sensed at PS1, the tape motor is turned off and the tape is taken away by
the printer transport. the tape drive roller contains a one-way clutch that
minimizes the drag on the tape being taken away by the printer transport.
The tape motor is connected to J117 on the main logic board.
3.4 Envelope/
Tape Transport
✍
TIP: See section 3.10
for DM475 differences
and specific theory.
Figure 3-4A Tape Feed Unit
Tape Motor
Tape Drive Roller
Gear Train
Tape Trans-
port Roller
Exit
Roller
Tape
Strip
Figure 3-4B Tape Feed Path