IBM Selectric I/O Manual Of Instruction page 51

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The camming surface or lobe on the print cam that produces
the greatest impact velocity is called the high velocity lobe.
This is the right hand lobe on the print cam. The left hand
lobe (producing less impact velocity) is called the low veloc-
ity lobe (Fig. 105.2).
The roller is: positioned (left or right) under either camming
surface of
t~e
print cam by the print cam follower roller yoke
which straddles the roller (Fig. 105.3). The yoke is mounted
on a pi n that protrudes from the tab cord anchor bracket as-
sembly. The yoke is also free to sl ide left or right on its
mounting pin.
FIGURE 105.3 Print Cam Follower Roller Yoke
A lever, which controls the lateral position of the yoke and
roller, mounts on the tab cord anchor bracket by a shouldered
rivet. This lever is called the yoke actuating lever (Fig. 105.4).
The yoke actuating lever is spring loaded at the rear in a
clockwise direction (observed from the bottom of the ma-
chine) by the yoke actuati ng lever spring. This spring ten-
sion positions the roller directly beneath the high velocity
lobe of the print cam as shown in (Fig. 105.4).
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41.1
Yoke Actuating Lever
Tab Cord Anchor
Bracket
I'
Velocity Contro'l
Cable
I,;.::;
~<.:;.,:\
:-"
',: .. ;.;,; I , __
I
~., I
. 1
I"
I. :
l.l' Z
C':2200r0 ..=;.='
2'~J
FIGURE 105.4 Yoke Actuating Lever And Spring
A sheathed cable called the velocity control cable fastens
to hooked portion of the yoke actuating lever (Fig. 105.4)
0
Whenever a pull is produced on the velocity control cable,
the yoke actuati ng lever wi II rotate counterclockwise,
(stretching its spring) shifting the print cam follower roller
from the high velocity lobe to the low velocity lobe of the
print cam as shown in (Fig. 105.5).
I---J
. 1
!i..:
·:1
,,;,':"1
F'
'J
Pull Produ~ed
On Cable;.
i
Roller Shifts
To the Left
\.
":-""
'-'~'\"
1
Yoke Actuating , :
:r:"'"
d
r.
1
Lever Spring : :
1'1
I 1
' l
1 1
t~=~-,-T--=-·~ =~;...-~-_-_~~)
FIGURE 105.5 Low Velocity Operation
When the pull on the velocity control cable is relaxed, the
yoke actuati ng lever spri ng shifts the roll er back to the ri ght,
positioning it under the high velocity lobe of the print cam
(Fig. 105.4).