Epson U375 - TM B/W Dot-matrix Printer, Technical Manual

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2-4
■
Platen movement
The platen is normally inside the guide frame set. When
current is supplied to the platen switching solenoid during
printing, the steel core is pulled in the direction of
➡
A, and
the lever linked to the steel core is pushed in the direction
of
➡
B. The linked lever spring positioned between the
linked lever and the platen holder pushes the platen outside
of the guide frame set (in the direction of
➡
C), and the
appropriate platen gap is maintained.
Figure 2-10. Platen Operation
2.2.3 Detection Mechanism
Each of the detection component mechanisms in the TM-
U375 and their corresponding functions are listed below.
Detailed explanations of each of the detection mechanisms
are provided in this section.
Table 2-1. Detection Mechanism and its Function
(
✽
) The near-end and cover open sensors are located in the
case and are not attached to the printer mechanism.
Function
Initial setting of TM-U375
Detection of head carriage
operation abnormality
Detection of presence/absence
of slip/validation paper
Detection of presence/absence
of paper on the paper roll
Detection of cover open/close
Detection Mechanism
• Home position
• Carriage motor out-of-
phase state
• Cut sheet (TOF/BOF)
• Paper roll near-end (
✽
)
• Cover open (
✽
)
Figure 2-11. Sensor Mechanisms
■
Home position detection mechanism
The home position detection mechanism is located at the
left end of the carriage subset stroke. This mechanism
confirms the position of the carriage and detects any
abnormalities in its operation. Initial setting is performed by
sensing the detection plate on the rear left of the carriage.
The home position sensor consists of an LED and a photo
IC. When the carriage subset moves, the detection plate
moves between the LED and the photo IC. The beam of
light is then interrupted, and the output level of the photo IC
changes. This change in the output level is read and used
as the carriage movement position detection signal.
Figure 2-12. Home Position Sensor Circuit Diagram
CONFIDENTIAL