HP C8088B, Service Manual

Page: 71 / 300

ENWW Chapter 5 Theory of operation 69
8-bin mailbox
Main modules
The 8-bin mailbox has 9 bins for sorting and handling printed media. The topmost bin receives
the media face-up as it comes from the printer. The remaining eight bins receive the media face-
down. The destination bin for the printed media depends on the device operating mode and the
presence of media. The top bin in this 8-bin group can be configured as a copier bin, and used
exclusively for copies from an MFP.
The 8-bin mailbox has several subassemblies or mechanical parts that work together to perform
the paper-handling function:
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Flipper—The flipper is the assembly at the 8-bin mailbox entry point. It receives the sheets
from the printer and then delivers them to the face-up bin or flips them for deliver to the face-
down bins. The flipper has a moving input paper guide that latches into the printer or MFP
exit to provide a continuous paper path.
●
Belt—The transport belt system is a vertical mechanism that takes the sheets that the flipper
assembly flips and moves them down to the elevator head for delivery to the face-down bins.
The system consists of a rubber belt and a flexible sheet-metal guide. The sheets are
pressed between them for transport.
●
Delivery head—The delivery-head mechanism is the most complex part in the 8-bin mailbox.
It positions the elevator head in front of the bin where a sheet is to be delivered. The eject
system is included in the elevator head. The eject system has two sensors in its path: one for
detecting a sheet that is arriving from the belt (EXIT1) and one for detecting a sheet that is
about to be ejected (EXIT2). A single stepper motor drives the sheet for ejection. Another
stepper, called the slider, positions a group of rollers to feed into the bins. The rollers are not
fixed, because they hit the bins when the head moves up or down. Instead, they retract when
the head moves, and extend into the bins after the head stops. A single sensor indicates the
position of the slider.
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Bins—The 8-bin mailbox has a total of 9 bins. The topmost bin holds media that is delivered
face-up, and the lower 8 accept face-down delivery. The bins have no moving parts, but the
face-down bins use a system of slots and lever flags that the elevator reads to indicate
where it is positioned, the bin capacity, the presence of media, and bin-full conditions. In
order for the sensors to read valid information, the bins must be correctly placed. The
operation of the delivery is especially sensitive to misplaced bins. Note that the lever flag for
each bin is mounted in the bin directly above it.
●
Controller PCA—The controller PCA or main board is attached to the bottom of the 8-bin
mailbox, with the internal wiring and harnesses routed vertically along the inside of back
cover.
●
Power supply—A universal power supply is activated when the printer or MFP power switch
is turned on. The printer or MFP paper-handling controller sends a power-on signal to the
power supply on the 8-bin mailbox through the controller PCA. The power-supply circuit
pr24 V for motors and +5 V for sensors and controller electronics. The power supply
is also activated when the controller PCA is set to service mode.