IBM Selectric I/O Manual Of Instruction page 52

Whenever a low velocity character is selected, (at the key-
board) a pullan the velocity control cable is produced to
shift the roller to the low velocity lobe on the print cam.
This pull on the cable is initiated at the keyboard. When
anyone of the selector interposers that are in positions 32,
36, 38, 39, or 42 are powered forward by the fi I ter shaft,
a knob on the forward end of that interposer contacts an up-
right lug on the low velocity vane causing it to rotate for-
ward (Fig.
105.6).
Selector Interposer
Low Velocity Vane
Bellc:rank
~
• FIGURE
105.6
Low Velocity Selection
The left end of the low velocity vane pivots in a mounting
bracket fastened to the top surface of the front keylever guide
comb support. The right end of the vane pivots in a hole in
the right hand keyboard sideframe. (The vane extends only
half way across the keyboard.) The laterol position of the
vane is controlled by a C-clip located on each side of the
vane mounting bracket.
The low velocity vane bellcrank is fastened to the right end
of the vane outside the keyboard side frame (Fig. 105.6).
Rotation of the vane and bellcrank, during a low velocity
operation, creates a pull on the link causing the low velocity
latch to rotate counterclockwise about its mounting stud. The
rotation of the latch swings it out of the operating path of an
adjustable stop on the low velocity cam follower. The cam
I
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\..,
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Adjustable Stop
•
Cable Clamp
FIGURE 105.7 Machine
,lilt
Rest
•
•
follower and the adjustable stop operates as one piece pivot-
ing about a stud on the keyboard sideframe (Fig. 105.7). A
heavy spring hooked to the adjustable stop and anchored to
the latch mounting stud, spring loads the follower in a clock-
wise direction.
The velocity control cable is hooked to the lower extension of
the follower. The upper extension of the follower is spri ng
loaded against the low velocity cam which is a double-lobed
cam set screwed to the right end of the fi Iter shaft directly to
the left of the shift interlock cam (Fig. 105.7). The radial
position of the cam is set so that the cam follower will
be
on
the high part of one of the cam lobes when the fi Iter shaft is
at rest. Whenever the follower is allowed to follow the con-
tour of the cam towards its low point, a pull will be produced
on the velocity control cable by the heavy spring load on the
follower.
(
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\..
,-
- \ I)
~
__
_ /
---
-
--,
r
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'- _ _ _ _ J
r-\ \ \ ....
~ ~
_1 \ ':...
"Latch Swings Out Of The Way:,--9
',-
FIGURE 105.8 Beginning Of A Low Velocity Operation
The cam follower will begin to follow the contour of the cam
towards its low point whenever the low velocity latch is ro-
tated out of the path of the adjustable stop as shown in Fig.
105.8).
This occurs each time a low impression character is
selected at the keyboard.
(Fig.
105.,9)
shows the low velocity cam follower riding down
toward the low dwell of the low velocity cam, thereby caus-
ing a pull to be produced on the velocity control cable. Note
that the low velocity latch is attempting to restore back to its
rest position but"ccinnot fully restore until the cam follower is
powered back to its rest position. The latch restoring spring
between the latch and the adjustable stop provides the restor-
ing action not only for the latch but for the low velocity vane
also.
---
""
/
- ",-
- -
-
.
' -
__ - - c)
Low VelOCIty Cam
~
-=
Follower _____
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V
C]
'-.... ---: - r"\
''::
/---
--
(
-- ------ J
Latch Restoring Spring
Low Velocity
Cam
- - - - Pull Being Produced
FIGURE 105.9 Low Velocity Operation
41. 2