Transfixing, Stripping And Exiting - Tektronix Phaser 340 Service Manual

5
Theory of Operation
5-28 Phaser 340 Color Printer
Transfixing, stripping and exiting
As the leading edge of the sheet of paper trips the paper preheater exit sensor, it
starts the transfix roller being lowered to its transfix position. The process motor
rotates clockwise, rotating the process drive compound gear counterclockwise.
Fourteen flags on the circumference of the gear represent the fourteen teeth on
the small gear, on the back of the compound gear. When the teeth of the small
gear are in the proper position, as detected by the compound gear position
sensor, the transfix cam solenoid (located on I/O board 3), energizes to release
the spring-loaded transfix cam on the right end of the transfix roller shaft. This
allows the transfix roller gear (which up to this point in time had missing teeth
"disengaged" to the 14-tooth gear of the process drive compound gear), to rotate
slightly and engage the small gear of the compound gear. During this time, the
drum, rotating at about 24 rpm, positions the deadband to coincide with the
arrival of the leading edge of the sheet of paper (which is moving at the same
rate as the drum).
The rotating transfix gear rotates the transfix roller shaft about one-half
revolution. The transfix roller, which is eccentrically mounted on the transfix
roller shaft, rotates into contact with the paper (5 mm behind the leading edge)
and then stops. This sandwiches the leading edge of the paper between the
transfix roller and the beginning of the image on the drum. The drum's rotation
rotates the transfix roller and begins to pull the sheet of paper between them. At
this point, the transfix roller shaft rotates slightly so a lobe on the transfix roller
cam pushes the exit roller gear train into contact with the ring gear on the right
end of the drum. As the drum rotates, the exit rollers rotate. The transfix roller
shaft rotates slightly more so a protrusion on the transfix roller cam causes the
stripper fingers to momentarily drop down onto the deadband of the drum and
catch the leading edge of the sheet of paper and direct the paper to the rotating
exit rollers. The transfix roller shaft rotates slightly more to clear the protrusion
on the transfix roller cam and raise the stripper fingers so they no longer contact
the drum.
The process motor stops, leaving the transfix roller cam in its half-rotated
position. Friction from the rotating drum continues to turn the transfix roller,
which freely rotates on the transfix roller shaft. The ink on the drum transfers to
the sheet of paper pulled by the friction between the drum and the transfix
roller. After about 1.8 seconds, the complete image has been transferred to the
paper and the transfix roller is lifted off of the drum.