Ribbon Shift Mechanism - Epson LX-300 Service Manual

Operating Principles

2.1.5 Ribbon Shift Mechanism

This printer can be equipped with a color upgrade kit to print in color. The printer performs color
printing unidirectionally. The option is composed of the color ribbon shift mechanism. The Color
ribbon feed mechanism is shared in common with black ribbon feed mechanism, and the shift
mechanism shifts the ribbon cartridge up and down.
Table 2-2 shows the CS motor assembly specifications. The motor control system is open-loop, so
that when the color is being changed, the positioning is controlled by stepping pulse.
Table 2-4. CS Motor Assembly Specifications
Category
Type
Drive Voltage
Coil Resistance
Drive Pulse Frequency
Excitation Method
The ribbon shift mechanism consists of the color ribbon and color upgrade kit. The color upgrade
kit is composed of the CS motor assembly, ribbcm shift gear/cam, motor driver IC, and color ribbon
sensor. The l-inch-wide color ribbon is separated into four equal-width bands of different colors.
The ribbon shift mechanism shifts the ribbon cartridge up and down.
When the color ribbon cartridge is loaded, it is possible to print in up to seven colors. One of the
four colors on the ribbon is selected by the color ribbon cartridge motion, which inserts a portion of
the plastic posts into the slots in the printer mechanism as a fulcrum. Figure 2-9 illustrates the color
shift mechanism. The mechanism shifts the ribbon cartridge by converting the gear rotation to
liner motion (up and down) of the color ribbon cartridge, using color shift cam gear.
Any color band can be selected by' rotation of the CS motor assembly, using the color home
position (the position of the black color band) as a starting point and reference position. Home
position is recognized by the CS motor assembly stepping pulse. When printer is power on, the CS
motor assembly is exated at any phase position at first. Next, the CS motor assembly is turned for
235 steps ( black + yellow). Then, the motor returns one step (yellow+ black), and the 'motor is
stopped. Finally, the motor returns 223 steps (yellow+ black) and stops. This position is home
position.
Table 2-5 gives coloring sequences. For halftones, as shown in the table, a color is created by
printing one color on top of another.
Print Color
Magenta
Orange
Note: The printer prints the brighter color first to prevent the ribbon from bt ng stained
2-8
4-phase, 48-pole, PM-type stepping motor
35 VDC * 10Yo
150 ohms f
Color shift 500 pps
Constant-vottage 2-2 phase excitation
Table 2-5. Coloring Sequences
Print Ribbon
First Printing
Black Black
Magenta
Cyan cyan
Yellow Yellow
Green Yellow
Yellow
Violet
Magenta
LX-300 Service Manual
Requirement
(per phase, at 25° C or 77° F)
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cyan
Magenta
Cyan