Mainspring - IBM Selectric I/O Manual Of Instruction

A. REST POSITION
Trigger- Knockoff Eccentri c
Forces Trigger To Rear
B. ACTIVE POSITION
Escapement
Torque Bar
Escapement
Torque Bar
FIGURE 110. Escapement Trigger Operation (Late Style)
Carrier
pull causes the trigger to move down at the rear and operate
the torque bar.
Because the carrier is relatively light and moves quickly, the
escapement trip must not occur before the character print.
If it did, the carrier might move before the character printed
or might be moving when the character is printing. This
would result in an uneven left margin or poor horizontal
alignment and possible smearing of the character depending
upon the timing of the trip. To eliminate this possibility, the
escapement cam is timed so that the escapement trip occurs
just after the type head leaves the platen to restore to rest.
On 11 inch machi nes on Iy, a sma II eccentri c co liar on the
pivot pin (Fig. 106) prevents the pin from bowing forward
due to the pull of the escapement trip link. The collar braces
the pivot pin by resting against the bracket in which the piv-
ot pin is mounted. Without the collar, some of the trip link
motion wou Id 'be lost in the flexing of the pivot pin. Escape-
ment fai lure would result, if not enough trip link travel re-
mained to remove the pawls from the rack.
MAINSPRING
Any time the escapement and backspace pawls are removed
from their racks, the carrier is pu lied toward the right. The
mainspring supplies the tension for a \I movement of the carrier
toward the right. It is located at the right rear corner of the
machine. Notched lugs of the mainspring cage fit into slots
in the backplate (Fig. 111). Tension of the mainspring is
changed by turning the entire mainspring cage to a new loca-
tion. When working with the mainspring, extreme care
should be taken to keep it under control.
Cord Tens ion Arm
FIGURE 111. Mainspring And Cord System
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