Typehead - IBM Selectric I/O Manual Of Instruction

Print Shaft
lFi I ter Shaft
FIGURE 6. Drive Mechanism
Through a series of idler gears at the left, two other shafts are
driven by the cycle shaft
~ach
time it operates (Fig. 6). They
are the filter shaft and the print shaft. The filter shaft oper-
ates the characterselectior.l mechanisms, the print escapement,
the shift interlock, and a spacebar lockout device. The print
shaft operates the print mechanism, type aligning mechanism,
and ribbon feed and lift mechanisms.
The shaft to the right of the cycle clutch pulley hub is the
operational cam shaft (Fig. 6). All powered functional oper-
ations are driven by its rotation. The functions involved are
spacebar, backspace, tabulation, carrier return, indexing, and
shift. The shaft also controls the speed of the carrier during a
tab operation. Each of the functions is discussed in detail in
its own section.
The operational cam shaft is driven by the cycle clutch pulley
hub and isin continuous rotation whenever the motor is running.
The right end of the shaft operates in a self-aligning porous
bronze bearing. The left end extends into the cycle c1utclh
pulley hub where it is supported by a vinyl sleeve (Fig. 7).
The sleeve provides a snug fit for the shaft in the hub to pre-
Cycle Clutch Pulley Hub
Torque Limiter Hub Sleeve
FIGURE 7. Operational Cam Shaft Drive Connection
3
vent any noise due to vibration. The driving connection
be-
tween the cycle clutch pulley hub and the operational shsft is
made by two extensions of the hub that fit into cut-outs in the
left side of the torque limiter hub. The torque limiter hub is
held in position at the extreme left end of the shaft by two set
screws. Two nylon inserts fit into the cut-outs of the torque
limiter hub (around the extensions of the cycle clutch pulley
hub). The inserts provide a noiseless driving connection
be-
tween the two hubs.
Just to the right of the torque limiter hub are three spring
clutches and two small pinion gears. These components are part
of the carrier return and tab mechanisms and are di~ussed in
their particular sections.
TYPEHEAD
Carrier Assembly
The printing element is a ball shaped typehead containing
eighty-eight characters. The type head is supported in front
of the paper by a framework called the carrier. The carrier
is the box-shaped casting that moves laterally just in front of
the platen (Fig. 8). Its purpose is to transport the type head
and other related mechanisms along the writing line. Almost
the entire print mechanism is contained within the carrier as-
sembly. In addition, the carrier also supports the ribbon, rib-
bon feed and lift mechanisms, and a bracket that controls the
left and right margins on the paper.
FIGURE 8. Front Carrier Support
At the front of the carrier, a sleeve fits into two bronze bear-
ings in the carrier (Fig. 8). The sleeve, called the print
sleeve, must rotate within the carrier. It also slides left to
right on the print shaft to provide the front support for the car-
rier. An oil soaked felt ring surrounds the print shaft and is
enclosed in a retaining cup at each side of the carrier. As
the carrier moves, the felt ring, called the print shaft wiper,
spreads a light film of oil on the shaft to lubricate the sliding
ofthe print sleeve. Oil from the print shaft wipers is also ab-
sorbed by the bearings in the carrier casting to lubricate the
rotation of the print sleeve.