Operational Selection Unit - IBM Selectric I/O Manual Of Instruction

As the cam follower is operated, the interposer is restored to
the front by the restoring lever. This causes the spring be-
tween the interposer and the operational latch to extend
(Fig. 119). Extending the spring tends to pull the latch out
from under the cam follower before the operation is completed.
To insure a complete operation, the latch is locked to the
rear as soon as the operation begins. As the latch is pulled
down by the cam follower
I
it moves down behind a lug of
the operati ona I control bracket (Fig.
120).
The lug prevents
any forward movement of the latch until the operation is com-
pleted and the cam follower restores. The latch is then
pu lied forward into its rest positi on against the interposer.
The carrier return latch is not locked to the rear, because
its beveled forward edge permits it to remain in contact with
the interposer throughout the operation (Fig.
117).
Operational
Interposer
Operational Latch"
FIGURE
120.
Operational Latch Locked To The Rear
6. Operating Sequence
As the desired keylever is depressed, a lug of the keylever
pawl contacts an interposer forcing it down to release it from
the guide bracket. The interposer is pulled to the rear by its
spring. A lug on the interposer contacts the clutch release
arm rotating it down at the front to allow the cam clutch to
be engaged. At the same time, the interposer forces its se-
lective latch to the rear pushing it under the cam fo) lower.
The cam is driven by the clutch ratchet causing the cam
follower to move from the low point to the high point of the
cam. Movement of the cam follower pulls down on the op-
erational latch to power the mechanism and, at the same
time, actuates the interposer restoring lever to restore the
interposer forward. The clutch release arm restores into the
path of the clutch wheel ready to disengage the cam clutch.
The cam follower passes the high point of the cam and re-
stores to the rest position as it reaches the low point. The
operational latch is snapped forward against its interposer into
the rest position and the operation is completed.
OPERATIONAL SELECTION UNIT
This unit is mounted to the power frame directly below the
operationa I interposers and consists of a magnet unit and a
contact assembly (Fig.
121).
49
SCREW LINK
FIGURE
121. Operational Magnet Unit
Magnet Unit
The magnet unit contains five magnet assemblies, one for
each operational interposer. The magnets are mounted to a
bracket that is fastened to the power frame (Fig.
121).
When the armature is attracted, it moves away from the
power frame pulling down on a link (Fig. 122).
This causes an interposer to be tripped without moving a
keylever. The slotted head on the lower end of the link pro-
vides a means of adjusting the link without removing either
end. The link extends through a hole in the armature, and
' -_ _ _
._---t~::r--Interposer
Screw Link
-------~] Armature
N yl on Washer
Magnet --I-I~""
FIGURE
122.
Operational Magnet Operation
the upper end is connected to the interposer by a clevis. A
crowned nylon washer serves as
d
bearing point between the
armature and the head on the link. This allows the top of the
link to move front to rear with the interposer without changing
the effective length of the link. Once the interposer is
tripped the operational control is the same as previously de-
scribed.