Paper Pick And Measurement - Tektronix Phaser 380 Service Manual

5
Theory of Operation
5-22 Phaser 380 Color Printer

Paper pick and measurement

Pick . The paper-pick solenoid is momentarily energized to release the clutched
paper-pick roller and allow the pick roller to rotate with the process gear train
for one revolution. The lower feed roller electric clutch is also energized so the
lower roller rotates with the process gear train. The process motor rotates
forward rotating the paper-pick roller one revolution. This pulls one sheet of
paper out of the tray and up into the rotating lower paper feed rollers. The
rotating lower feed roller continues to pull the sheet of paper from the paper
tray. The handfeed/paper pick sensor detects the leading edge of the sheet of
paper as it enters the lower feed rollers. If the leading edge of the paper is not
detected, then the paper pick cycle is attempted one more time. If the attempt
fails, a paper pick jam is declared.
Aligning. As the leading edge of the paper passes through the lower feed rollers
it passes before the media width sensor. Once detected, the paper advances
against the nip of the upper feed rollers, which are not rotating. This creates a
buckle in the paper. The lower feed roller electric clutch is turned off and the
upper feed roller electric clutch is turned on. Next, the process motor reverses
for a moment to drive the upper feed rollers backward, aligning the paper to the
paper path. The lower feed roller electric clutch is turned on and the process
motor rotates forward to pull the now-aligned sheet of paper forward to the
paper preheater.
Measurement. Having detected the leading edge of the paper, the media width
sensor, driven by the media width sensor motor through a screw drive, travels to
the left until it detects the left edge of the paper. Reversing and verifying this
point, the media width sensor travels the width of the page until it detects and
verifies the right edge of the paper. Finally the paper width sensor positions
itself slightly inward of the right edge of the paper so it can detect if the paper
skews as it moves through the paper path. If the media width sensor does not
detect either the left or right edge of the media, a feed jam is declared.
Knowing the left and right edges of the paper, the printer calculates the width of
the paper and, if the paper is hand-fed or is a standard size sheet drawn from the
tray, the image to be "printed" on the drum is positioned so it prints on the
lower-left of the sheet of media with a margin of 5 mm (left) and 9 mm (bottom)
Oversized images are clipped, if necessary to fit on the paper with minimal
margins. For non-standard paper sizes drawn from the tray, the measurement is
used to determine if transfixing (the image will already be deposited on the
drum) will be allowed or a media size error declared.
An image is deposited on the drum only after the first sheet of media in a newly
installed tray is measured to ensure that the media size sensors correctly indicate
the size of the media in the tray. All images afterwards are deposited on the
drum, before media measuring takes place to lower print times. Measuring is
always preformed on a manually-fed print job before image deposition on the
drum to confirm the media matches the size the printer was expected to be fed.