HP Color LaserJet CM4730 Service Manual - Page 211
Pickup/feed unit, Cassette detection and cassette media size detection
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Pickup/feed unit The pickup/feed block is structured with two blocks. One is the pickup block, which picks up media from the cassette or the multipurpose tray into the MFP one by one. The other one is the feed block, which feeds the picked-up media to the fuser. The following sequence of events occurs: 1. The DC controller rotates the pickup motor (M9), drum motors (M1, M2, M3, M4), ETB motor (M7), and fuser motor (M5) after receiving a print command from the formatter. 2. The feed roller and the registration roller rotate as the pickup motor starts to rotate. The cassette separation roller also begins to rotate. However, the separation roller does not rotate. 3. Media is picked from the cassette. The cassette pickup solenoid (SL2) is turned on after a specified time after 'scanner ready'. This rotates the cassette pickup roller and cassette feed roller to pick up media in the cassette. Media is picked from the MP tray. The MP pickup solenoid (SL1) is turned on after a specified time after 'scanner ready'. This rotates the MP tray pickup roller to pick up media in the tray. 4. Any multiple-fed media is removed by the cassette paper separation roller (paper separation pad for the MP tray) and a single sheet is fed to the registration roller. 5. The skew of the media is corrected by the registration shutter. The media is then fed at its prescribed speed. The formatter specifies the feed speed depending on the media type. 6. Toner is transferred to the media on the ETB, and the media is fed to the fuser/delivery block. Cassette detection and cassette media size detection The MFP can sense whether a cassette is installed correctly, and it can sense the size of the media in the cassette. Paper-size detection switches at the back of the cassette send this information to the DC controller. The DC controller determines which size is loaded by reading various switches. Table 4-6 Paper tray media size detection Paper size Paper-size detection switch CNT0 CNT1 CNT2 A4 on off off B5 on on off A5 off on off Letter on off on Legal off on on Executive off off on Custom on on on No paper tray off off off Although the cassette determines the media size by reading the switches, the user could select a different size from what is loaded, creating an error in media-size detection. The paper leading-edge sensor detects when the leading edge and the trailing edge of a sheet pass it. By measuring the time between the passing of the leading edge and trailing edge, the sensor can ENWW Pickup/feed system 191