IBM Selectric - Page 71

7.
Escapement Trip Link
Cam
Follower Just Resting At Low Point
FIGURE
151. Escapement Cam And link Adjustment
Check the adjustment by holding the cycle clutch check
pawl out of the way so that the cycle shaft can be ro-
tated backward. Rotate the fi Iter shaft gear backward
slightly and observe that the escapement trip link moves
forward immediate Iy. This wi II insure that the escape-
ment cam is not resting past the low point. To insure
that the cam follower has fully reached the low point,
hand-cycle a print operation. The escapement trip link'
should not move during the first part of the cycle.
The cam adjustment affects the timing of the print es-
capement. Advanced timing could cause the trip to
occur before the print action, resulting in crowding or
blurring of the printed characters. Retarded timing wi II
cause the cam follower to rest part of the way up the
incline of the cam. This could restrict the escapement
trigger from resetting over the torque bar lug as the
filter shaft returns to its rest position. The spacebar
mechanism wou Id then be disabled.
On machi:nes equipped with the old style spacebar lock-
out mechanism, the lockout cam adjustment must be
checked each time the escapement com adjustment is
changed. Advancing or retarding the escapement cam
could allow the lockout cam to disable the spacebar
mechanism.
CAUTION: On machines equipped with the old style
spacebar lockout mechanism, a lateral position of the
escapement cam on the fi Iter shaft must be maintained.
When the machine is at rest the lateral position of the
escapement cam shou Id a !low .050 II to .060 II left to
right movement of the spacebar lockout cam.
Escapement Trip Link - Adjust the trip link so that a
clearance of .007
11
to .010
11
exists between the torque
bar lug and the hook of the escapeme!nt trigger in the
rest position (Fig. 151).
CAUTION: In adjusting the escapement trip link be
sure
that the trigger lever stop (if present) and the ad-
justable screw in the spacebar latch lever do not re-
strict the upward travel of the trigger lever. (Reference
Spacebar mechanism adjustment #2.)
The adjustment insures that the torque bar will always
8.
2-53
be rotated far enough to tri p the pawls from thei r
racks.
If excessive clearance is present, the escapement may
eventually fail as wear occurs in the system and reduces
the amount of travel given to the trigger.
Insufficient clearance may prevent the trigger from re-
setting over the torque bar lug. at the end of each
cyc Ie. It maya Iso cause the escapement tri p to occur
too early in the cycle. The trip shou Id not occur be-
fore the print action.
Escapement Trigger Action - Adjust the trigger guide
(early style machines) or the trigger knock-off eccentric
stud (late machines) so that the escapement trigger
wi II become di sengaged from the torque bar I ug when
the escapement pawl clears the rack by .010
11
to .011')"
(Fig. 152).
.010
11
to
-----
Trigger Disengages
From Torque Bar When
Correct Pawl Clearance
Exists
Trigger Guide
EARLY
Trigger Knock-Off Eccentric
LATE
FIGURE 152. Escapement Trigger Guide Adjustment