Paper Width Sensor - Epson Stylus Pro 9000 - Print Engine Service Manual

EPSON Stylus Pro 9000
To maintain a constant distance between the printhead nozzles and the paper,
the printer measures the thickness of the paper and adjusts the height of the
carriage accordingly. The printhead has three platen gap (height) settings, as
described in the table below.
Table 2-1. Platen Gap Settings
Platen Gap Setting
PG "Small"
PG "Medium"
PG "Large"
The actual platen gap position used during printing depends on both the
detected paper thickness and the user's paper thickness setting on the control
panel.
Table 2-2. Platen Gap Setting Determination
Control Panel Setting Paper Thickness Sensor
Wide
Auto
The printer uses two sensors in setting the platen gap:


Paper Thickness Sensor
This sensor physically gauges whether the paper falls into the normal/thin
category or the thick category. The Pressure Roller unit closest to home
position has a thin metal flag on top. When the Paper Release Lever is in
the Lock position and thin paper is loaded, this flag pivots into the space
between the sensor's light emitter and receiver. However, when thick
paper is loaded, the flag is forced forward out of the sensor area.
Sensor signal = ON at 0.7 V or less: Normal or thin paper
Sensor signal = OFF at 2.4 V or more:Thick paper
Technical Overview
Gap Distance
1.3mm
2.2mm
2.7mm
Platen Gap Position
Wide PG "Large"
Standard PG "Medium"
Wide PG "Large"
Standard PG "Small"


PG Sensor
This light-reflecting sensor detects whether the subcarriage is in the thick
paper position or normal paper position. The PG Gear rotates with the PG
Cam, and the PG Sensor determines the subcarriage's position from the
position of the PG Gear, using the hole in the gear's side as a reference.

PAPER WIDTH SENSOR

This sensor locates the right and left edges of the paper. The light emitted from
the sensor is reflected back to the sensor where paper exists. In this way the
sensor determines where the paper's edge is and how wide the paper is.
Left
edge
Paper
Figure 2-6. Paper Width Sensor
Carriage
Right
edge
HP side
Paper Width
sensor
25