IBM Selectric I/O Manual Of Instruction page 20

Selector Latch
FIGURE 35. Keyboard Section and Character Selection
Adjusting lugs just to the rear of the top row of keybuttons make
it possible to adjust the relative height of each individual key-
lever and keylever pawl.
Interposers
Each keylever
ha~
a character interposer located just below it
(Fig. 35). The purpose of the interposers is to select the amount
of ti It and rotate needed to bring the desi
re~d
character to the
printing point. A large fulcrum rod passes through an elongated!
hole in the front of each interposer and provides a support on
which the interposers can pivot and sl ide. A guide comb at
the front and rear separates the interposers. The interposers
are allowe-dtomove up and down in the rear guide combaswell
as front to rear. An extension spring from each interposer to
the top of the rear guide comb .loads the interposer to the rear
and up into the rest position.
The interposers have
~several
lugs extending from them, each
with its own operation to perform (Fig. 36). Each interposer
has a lug on top in position to be struck by the keylever pawl.
On the bottom of the interposers
ar~
positions for eight lugs.
Seven of the lugs are selective lugs. The obsence or presence
of these lugs in different pO,sition combinations makes the inter-
posers different. There are no two alike. The rearrnost selec-:-
tive lug is for special applications of the machine.
Keylever Pawl Contact Surface
Latching Surface
Rl R2 R2A R5 Tl 12
c~
o
~~
Filter Shaft
S I L
Contact Surface
e ector ug Cycle Clutch Release Lug
F I GU RE 36. Se I ector Interposer
13
One lug on the bottom is common to all interposers. It is a
wide lug located at the middle of the interposers. Its purpose
is to release the cycle clutch for a cycle operation whenever
a keylever is depressed. Directly below the lug is the cycle
bail that pivots up and down (Fig. 35). Downward movement
of any character interposer forces down on the cycle bail to
release the cycle clutch latch and allow a cycle operation.
The cycle clutch release lug is cut at an angle on the bottom
to prevent interference between the lug and the cycle bail as
the parts are restoring to the rest position.
Fi Iter Shaft
When the interposer is depressed it pushed the cycle bai I down
to unlatch the cycle clutch and cause a 180
0
rotation of the
cycle shaft (Fig. 35). Rotation of the cycle shaft 180
0
also
rotates the fi Iter shaft 180
0
•
The fi Iter shaft is a two-bladed
shaft located at the rear of the keyboard section and just be low
the ends of the interposers. It rotates ina beari ng at each
end and is connected by a gear trai n on the left si de of th(
cyc Ie shaft.
When an interposer is depressed, the rear of the interposer is
moved down in front of one blade of the fi Iter shaft. As the
filter shaft turns, the blade drives the interposer forward to
operate the character selection mechanism.
Interposer Latch Spri ngs
Resting against the rear of each interposer is a spring finger
called the interposer latch spring (Fig. 37). The spring fingers
are slightly deflected to the rear when the interposers are at
rest. When any interposer moves down at the rear, the spring
snaps forward over the interposer and holds it down. The inter-
poser remains down until it is pushed forward enough to
cl'~ar
the spring finger. At that time it is raised and restored by its
extension spring.