Epson TM U200D - B/W Dot-matrix Printer, Technical Manual

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2-10 Mechanism Configuration and Operating Principles Rev.B
Paper detection mechanism
The paper detection mechanism is located in the paper path. The mechanism provides end
detection of the paper roll and semi-automatic loading by detecting presence or absence of the
paper roll when it is inserted. Since the paper detector switch sub assembly is a micro switch, it
is always ON when the paper roll is loaded.
Near-end detection mechanism (optional)
The near-end detector ass’y consists of the Lever, N.E. detection and a microswitch detector and
is located on the right side of the Case, lower. This detector detects the amount of paper left on
the paper roll.
The tip of the Lever, N.E. detection is always pressed against the edge of the paper roll by a
spring inside the microswitch. Therefore, when there is a large amount of paper remaining on
the roll, the Lever, N.E. detection is pressed against the side of the paper roll as depicted by the
solid lines in the figure below. This keeps the microswitch turned on. When the amount of paper
left on the roll decreases below a predetermined amount, the tip of the Lever, N.E. detection no
longer presses against the side of the roll and moves in the direction indicated by the arrow into
the hole in the center of the roll core. This turns the microswitch off and generates a signal
indicating that the paper roll is near its end.
Ribbon Switch Mechanism Unit
The ribbon switch mechanism unit consists of the Motor, carriage ass’y, Carriage sub-ass’y,
Tension plate ass’y, Pulley, belt tension, Home position detector ass’y, Frame, ribbon ass’y,
Spring, ribbon frame, Lever, ribbon switch, Lever, ribbon release and Spring, ribbon release.
The mechanism unit is placed at the left and right of the Carriage sub-ass’y, the position of
which is controlled by the number of Motor, carriage steps, with the home position as the
reference position. It switches between the black and red ribbon in the ribbon switch and ribbon
release areas outside the printing area.
Figure 2-13 N.E. detection mechanism
Paper roll center
Case, case
Microswitch
Lever, N.E.
detection
Paper roll