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Principles of Operation
Ribbon Transport System
Right Ribbon Guide
Hub Locking
Latch
Left Ribbon Guide
(Not Shown)
Ribbon
Spool
Ribbon
Motors
Ribbon
Ribbon Hub
Figure 14. Ribbon Transport System
An inked ribbon winds and unwinds continuously on a pair of spools latched
to hubs that are driven by the ribbon motors. The hubs and spools are offset
vertically to equalize ribbon wear and prolong ribbon life. The ribbon motors
operate only when the shuttle assembly is moving. Ribbon motion reverses
when a metal strip at either end of the ribbon crosses the left or right ribbon
guide, completing a circuit that causes both motors to reverse direction.
Constant ribbon tension is maintained by controlling each motor with a drive
or drag circuit. While the shuttle assembly is in motion, one motor acts as a
drive motor, pulling the ribbon against the resistance exerted by the other
motor—the drag motor. This system maintains a constant motor speed and
ribbon tension.
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