HP Pro 4300 C9H70UT C9H70UT#ABA manual Lifter-driver operation, Multiple feed prevention

Lifter-driver operation

The lifter driver keeps the media stack surface at a specific level in order to have a stabilized pickup operation regardless of the size of the media in the tray 2 cassette. The DC controller PCA operates the lifter driver motor (M103) for 50 seconds. The motor stops when the paper stack position sensor (PS107) detects the media. If the paper stack position sensor does not detect any media within 8 seconds after the lifting operation has begun, the DC controller PCA determines there has been a lifter driver motor failure and a message appears on the control- panel display (see “Alphabetical printer messages” on page 258 or “Numerical printer messages” on page 274). The DC controller PCA stops the lifting operation if the paper stack position sensor detects the absence of the tray 2 cassette.

Multiple feed prevention

The printer uses the separation roller in tray 2 to prevent multiple-feeding. Normally, the separation roller rotates in the same direction as the feed roller. The separation roller is equipped with a torque limiter, but because the force of the feed roller exceeds that of the torque limiter, the separation roller is actually driven by the feed roller.

If multiple sheets of media are picked up, however, the low friction force between the sheets weakens the rotational force from the feed roller to the separation roller. Consequently, the torque limiter takes control of the separation roller, and rotates the separation roller in the reverse direction, which removes the extra sheets.

Feed roller

Driving force transmitted from the feed roller

Pickup roller

Media

Separation roller

Driving force transmitted from the motor through the torque limiter

Normal

Multiple feed

Figure 19. Multiple feed prevention

84 Theory of operation Q2431-90912