HP LaserJet 4250 Service Manual - Page 146
Envelope feeder, Envelope-feeder pickup and feeding
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Envelope feeder The envelope-feeder driver controls the envelope feeder operation sequences. An 8-bit microprocessor in the envelope feeder driver controls the envelope-feeder sequence and the communication with the dc controller PCA. The dc controller PCA sends the pickup command to the envelope-feeder driver with the necessary timing. The envelope-feeder driver activates the solenoid in response to the command. The printer delivers a charge of +24 Vdc to the envelope feeder, which then generates +5V for the integrated circuits. Figure 5-15 Envelope-feeder I/O block diagram Envelope-feeder pickup and feeding In the envelope feeder, the envelope sensor (PS901) detects the presence of envelopes and the envelope-size sensor (PS903) detects the width of the envelopes. The envelope pick-up motor (M901) drives all of the rollers in the envelope feeder. When the dc controller PCA sends a print command, the main motor (M101) begins to rotate. After the main motor initial rotation phase is completed, the scanner motor begins to rotate. As the scanner motor rotates, the envelope pick-up motor (M901) begins to rotate to drive the pickup roller, feed roller, and separation roller, and an envelope is picked up. The separation roller removes any additional envelopes and a single envelope travels to the printer. The registration assembly corrects any skew. The envelope travels through the printer paper path and is delivered to the output bin. 132 5 Theory of operation