IBM Selectric I/O Manual Of Instruction page 16

The under side of the upper ball socket is hollow and forms the
socket for a ba II joint connection (Fig. 24B). A dog-bone
shaped ba II joint fits into the socket over a pin that extends
through the socket. The ball joint is identical at both ends.
The lower end fits over a pin in the lower be II socket. These
two ball and socket connections act as universal joints to per-
mit the type head to be rotated and ti Ited at the same time.
/ --
~
Upper Ball Socket
( \
/\--~
"J.
_;--~~I ~
B~I
Joint )
\
)
~--
lower Ball Socket
FIGURE 24B. Rotate Mechanism - Rocker Portion
The lower ball socket is part of a shaft called the rotate shaft.
The shaft operates inside the hollow of the tilt sector tube and
extends well belowthetiltsectorpulley. (On the gearless tilt,
the tilt sector tube and the tilt pulley have been eliminated.
The rotate shaftoperatesdirectly inside the hollow of the yoke.)
On both styles the bottom of the shaft pivots in a hole in a
plate attached to the bottom of the rocker. This plate acts as a
bearing for the bottom of the rotate shaft. Attached near the
bottom of the shaft is the rotate pulley similar in operation to
the ti It sector pu Iley (Fig. 24B). By means of the upper and
lower ba II sockets and the ba II j oi nt, the rotate pu lIey oper-
ates to rotate the typehead in either direction.
As on the ti It mechanism, the rotate pu lIey is operated by a
stee I tape that passes around two side pu Ileys and attaches to
the carrier. When either of the side pu lIeys moves away from
the other, the typehead is rotated counterc lockwise by the pu II
of the tape. When either side pulley moves toward'the other,
the typehead is rotated clockwise by the tension of the rotate
pulley spring (Fig. 25).
The rotate spring is of the mainspring type enclosed in a sta-
ti onary cage, with the outer end of the spri ng attached to the
cage. The inner end of the spring is connected to a hub on the
rotate pulley. A spring of this type must be used here rather
than an extension spring as is used on the tilt sector pulley, be-
cause the typehead is required to rotate almost a full revolu-
tion.
The right hand rotate pulley is attached to the shift arm and
moves only during the shift operation; therefore consider it to
be stationary for the present. The left hand rotate pulley is
attached to the rotate arm. When the arm moves away from the
side frame, it exerts a pull on the tape to rotate the typehead
counterclockwise. This direction is known as the positive direc-
tion of rotation.
When the left hand rotate pulley moves towards the sideframe,
the rotate spring turns the rotate pulley rotating the typehead
in a clockwise direction. This direction is known as the nega-
tive direction of rotation.
Positive Rotate Differential
The rotate differential is much the same as the tilt differential.
The latches are operated by the latch bail if they are allowed
to remain to the rear under the bai I. Each operates with a di f-
ferent leverage for different amounts of rotation. Rotation of
upto five characters is sometimes required on either side of the
rest position. This requires more latches and levers than for a
tilt operation.
Rotate Spring
Shi ft Arm - - -___
FIGURE 25. Rotate Tape System
9