Paper Transport System - Printronix P7000 Series Maintenance Manual

While the hammer is in flight the coils are de-energized and their magnetic
field collapses, restoring the magnetic attraction of the permanent magnet in
the hammer bank. After striking the ribbon and paper, the hammer rebounds
and is recaptured by the permanent magnet. When the shuttle reaches the
end of a sweep, it reverses direction, the paper is micro-stepped upwards one
dot row, and the hammer springs print the next row of dots as the shuttle
sweeps in the opposite direction. All this happens extremely rapidly: hammer
re-firing in a 2000 lpm printer, for example, takes about 419 microseconds,
with the vertical paper movement between dot rows occurring in 2.10
milliseconds.

Paper Transport System

Tractor
Support
Shaft
Shuttle Cover
Assembly
A two-phase DC stepper paper feed motor, directed by the engine controller
(EC) on the controller board, drives two tractor sprockets by means of a
toothed belt linked to a pulley on the splined shaft. The stepper motor permits
extremely accurate vertical paper movement in 1/72 inch increments. This
drive configuration is designed for continuous, fan-folded paper from 3 to 17
inches wide and 1 to 6 sheets thick. To reverse paper movement (that is,
move it downward) a second motor opens and closes the platen by means of
a toothed belt linked to a pulley on the platen shaft. Opening the platen
prevents paper jams when paper direction is reversed after viewing the print
area, setting top of form, or allowing applications to overprint forms.
Paper Path
Paper Supports
Figure 63. Paper Transport System
Shuttle Drive Motor
Tractors
Vertical
Adjustment
Splined
Knob and
Shaft
Splined Shaft
Pulley
Paper Feed Timing
Belt (under the cover)
375