IBM Selectric I/O Manual Of Instruction page 90

always possible for the keyboard lock bellcrank to enter the
selector compensator. If a character is in storage when the
keyboard lock interposer is pivoted down, the keyboard lock
bellcrank stops against the top of the stee I ba I'Is (Fig. 179).
The light spring connecting the interposer to the bellcrank is
extended slightly.
Keyboard Lock Interposer
Moves Down Info The
Path Of The Filter Shaft
~
Character Interposer
Blocking Compensator
Keyboard Lock Bellcrank
Cannot Enter Compensator
FIGURE 179. Line Lock Blocked
By Stored Character Interposer
To be sure that the keyboard is locked before another char-
acter can enter storage, the keyboard lock be IIcrank is driven
into position by the keyboard lock interposer. The interposer
contains an elongated pivot hole the same ,as a character in-
terposer. A stud in the interposer is in position just above a
spring-loaded arm on the keyboard lock bellcrank (Fig. 179).
The arm is reli eved to permit downward mov,ement of the in-
terposer. When the keyboard lock interposer is down, it is
positioned in the path of the filter shaft (Fig. 179). As the
fi Iter shaft operates the stored character interposer, the key-
board lock interposer is also driven forward (Fig. 180). The
stud on the keyboard lock interposer cams the arm of the key-
board lock bellcrank down. The heavy extension spring be-
tween the arm and the bellcrank is extended and creates a
strong downward pull on thebellcrank (Fig. 180).
The keyboard lock bellcrank is then snapped into the selector
compensator at the earliest possible instant. The keyboard is
Both Interposers Driven
ForWard By The Filter Shaft
FIGURE 180. Keyboard Lock Interposer Operation
71
locked with the carrier at the margin stop position of one
space later depending upon whether or not a character has
been stored at the beginning of the line lock operation.
No type pi ling wi II occur as a result of a linelock failure,
because the margin stop does not block the movement of the
carrier. No operational keys are affected by the line lock.
The carrier may be moved through the line lock zone by use
of the spacebar, backspace, carrier return, or tabu lator. The
line lock is usually released by operating the backspace or
carrier return or by depressing the margin release keylever.
Moving the carrier to the left or right allows all the line lock
parts to restore and unlock the keyboard. Depressing the mar-
gin release keylever rotates the margin rack to move the bell-
ringer bellcrank out of the path of the line lock bracket.
This allows the line lock parts to restore to rest unlocking the
interposers.
The keyboard lock interposer is restored up and to the rear by
an extension spring the same as a character interposer. The
,stud on the interposer extends to the left under the keyboard
lockbellcrank in position to restore the bellcrank into the
rest position.
Line Lock - (Late)
On the new style line lock mechanism the keyboard lock in'-
terposer and its operation have been eliminated. It has been
found that a sufficient amount of spring tension can be placed
on the keyboard lock bellcrank, by the operation of the bell-
ringer bail, to snap the bellcrank into the compensator tube
at the earliest possible instant. The keyboard may still lock
one space late after the carrier reaches the right hand margin
because of the character storage feature.
The new line lock consists of two pieces, the keyboard lock
lever and the keyboard lock bellcrank (Fig. 181). Similar to
the old style, the bellringer bai I operates the keyboard lock
lever down (as the carrier approaches the right hand margin)
causing the keyboard lock bellcrank to be loaded into the
selector compensator tube by the tension of the spring be-
tween the lever and the bellcrank. The mounting of the bell-
crank and lever remains the same as the old style.
Note in Figure 181 that the bellringer bellcrank has been re-
designed and is now one piece as compared to the old style in
Figure 178. The new style helps to reduce lost motion be-
tween the line lock bracket and the bellringer bai I. Because
of this new style bellringer bellcrank, the entire margin rack
must tip each time the carrier is returned through the right
hand margin. The rear extension of the bellcrank must ride
up and over the camming surface on the line lock bracket
causing the margin rack to rotate too. A back-up spring is
added to restore the bellringer bail. The bellringer bail has
been redesigned to reduce flexing which caused loss of motion
at the contact. Lost motion caused a variation in timing.
The I ine lock bracket assembly has also been redesigned to
simplify the margin release operation at the left margin. The
mounting hole in the margin stop latch has been elongated.
This allows the stop latch to float to the left under its restor-
ing spring tension whenever the margin release is operated
while the carrier is against the left hand margin stop. This
eliminates the necessity of holding the margin release button
depressed unti I the carri er is moved to the left.