Xerox Phaser 6180 Service Manual page 73

Theory of Operation
However, when two sheets are fed concurrently, only the Feed Roller rotates.
The Retard Roller is coupled to a friction clutch that prevents the roller from
rotating due to extra force from feeding two sheets; this process allows the
upper sheet to pass by as the lower sheet is stopped by the friction with the
Retard Roller at rest.
The Retard Roller is pushed toward the Feed Roller by spring pressure, and
controlled by the Friction Clutch with which it is coupled.
Multiple Feed
Feed Roller (Takeaway Roller)
Feed Roller (Nudger Roller)
Retard Roller (Separator)
Friction Clutch
Retard Roller (Separator)
s6180-147
Phaser 6180 Color Laser Printer Service Manual 2-19