User manual

95.08.23.11.30
Color LaserWriter 12/600 PS Basics & Theory 1–91
The three sensors described below govern paper feed from the cassette.
PS302 and PS303 are also active in print cycles originating from the
multipurpose tray or optional sheet feeder. Each of these sensors is
contained on the cassette pickup board (P/N 922-1311). Two are
reflector type sensors and one is a conventional photo-interrupter
sensor.
PS301 (Photo-
reflector)
The presence of paper in the cassette is detected by the cassette paper
sensor (PS301).
Example: The animation shows the paper path for the final sheet of
paper in the cassette. Up through frame 57, the light emitted from
PS301 reflects off the paper and back to PS301. When the trailing edge
of the last sheet of paper passes this beam in frame 58, the beam
projects through a cutout in the cassette elevator plate and is no longer
reflected back to PS301.
PS302 (Photo-
interrupter)
After actuating the lever for the registration paper sensor (PS302), the
paper reaches the registration roller. Since the registration roller is not
rotating at this time, the paper stops, its leading edge is curled, and its
skew is corrected.
Example: The paper actuates the lever for PS302 and reaches the
registration roller in frame 19 of the animation.
PS303 (Photo-
reflector)
When a certain time period elapses after the paper has passed through
PS302, the registration roller clutch (CL3) is turned on to resume
feeding the paper. When the paper reaches the paper leading-edge
sensor (PS303), the pickup motor and paper stop.
Example: Up through frame 38, the light emitted by PS303 reflects off
a prism and returns to PS303. The leading edge of the paper breaks this
beam in frame 39.
The DC controller and the mechanical controller detect the registration
position on the transfer drum by the transfer drum top sensor (PS8).
This timing is used as reference to execute the print sequence. The
mechanical controller starts driving the pickup motor at a certain time
period after detecting the registration position of the transfer drum.
Thus, the paper resumes feeding so that its leading edge will synchro-
nize with the gripper on the transfer drum and also match the image
leading edge on the photosensitive drum.
Animation