Epson Stylus Pro 7400, Service Manual

Page: 153 / 428

EPSON Stylus Pro 7400/7800/9400/9800 Revision B
Operating Principles Print Mechanism Components 153
PLATEN GAP ADJUSTMENT UNIT
In order to maintain the print precision, it is necessary to maintain the carriage (= head)
mounting position so that it is always a constant distance from the surface of the paper.
In this printer, the print head nozzle surfaces and platen surface are variable
mechanisms so that the gap between the paper printing surface and the head nozzle
surface can be kept constant.
The carriage has a 2-body construction with a sub-carriage on which the print heads are
mounted attached to the carriage which forms the base. The sub-carriage moves in the
vertical direction with respect to the paper surface. This movable system uses a cam (=
PG). When the sub-carriage is in the HP position (= right end), the pump motor and the
gear mounted on the cam shaft engage, the motor’s rotation (reverse) drives the cam
and the sub-carriage is positioned at the proper gap position.
In order to maintain the distance between the print head nozzle surface and the paper
properly, the thicknesses of the paper used are classified into 5 levels for PG setting,
namely, minimum PG (0.8 mm), small PG (1.2 mm), medium PG (1.6mm), large PG
(2.1 mm), and maximum PG (2.6 mm).
The sensors used in the platen gap adjustment unit are explained below.
Figure 2-3. Carriage Mechanical Unit and PG Adjustment Unit
Slide Gear
Sub-carriage (Head Mounted)
Bearing (Roll Type)
CR Guide Rail
Carriage
PG (Head SLID)
Right Side of Carriage
Bearing (Roll Type)
PG HP Sensor
HP Detection
Flag
Pump Motor Drive Force
(CCW)
Right Side of Printer Mechanism