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link, its bellcrank, and the clutch unlatching link and causes
the carriage return tab interlock to rotate clockwise (viewed
from the top of the machine) (Fig. 56). Rotation of this inter-
lock is limited by the interlock eccentric stop which limits
the amount of engagement of the clutch lat,ch behind the clutch
lever (Fig. 61). The clutch latch bellcrank also rotates the
rebound check interlock to insure that the rebound check
lever is not in the operated position. At this time the carriage
return tape is pulling the carriage toward the left margin.
As
the carriage approaches the left margin, the left margin
stop contacts the margin control lever and moves it toward the
left (as viewed from the back of the machine) (Fig. 61). A
lug on the margin control lever rotates the margin control bell-,
crank, which performs three main functions.
First, it rotates the air cylinder bellcrank to actuate the air
cylinder plunger. This causes a vacuum on one side of the
plunger and compresses the air on the other side (Fig. 62).
This action retards the travel of the margin
contr~1
bellcrank,
allowing the carriage to decelerate gradually without slamming
noisi Iy at the margin.
Second, the
lTD
rgin control bellcrank releases the intermediate
pawl release lever from the pawl release bellcrank by knock-
ing the hook shaped extension ofthe lever off the lug of the
bellcrank. This action permits the pawl release lever to re-
store to its rest position, allowing the escapement pawl to enter
the escapement rack. This occurs approximately one space or
less from the left margin.
Third, the margin control bellcrank contacts the carriage re-
turn tab interlock and rotates it counter-clockwise (from the
top of the machine). The interlock moves the clutch latch
linkage and unlatches the clutch. All the clutch parts restore
to rest and the carriage moves a small distance to the left,
under main spring tension, to take the sliding motion in the
escapement pawl. This small distance is called overbank and
is controlled by the position of the margin rack, by controll-
ing the position of the escapement rack, when the escapement
pawl enters the rack. Clutch unlatching occurs just before the
travel of the carriage is stopped by the margin control lever
striking its final stop (Fig. 61).
Iv
the carriage return were immediately operated again, the
:second operation reduces to a line space operation. This
means that the carriage wi II retain its position, but the platen
will be rotated to place. the paper on a new writing line. The
escapement pawl is not removed from the escapement rack
and the clutch latch does not engage the clutch lever. How-
ever, the carriage return cam completes its rotation and brings
the clutch surfaces together momentari Iy. The carriage return
tape pulls on the line space mechanism to index the platen.
Since the carriage is already at the margin, the margin con-
trol bellcrank is in the operated position, holding the hook
on the intermediate pawl release lever away from the lug on
the pawl release bellcrank. The pawl release bellcrank ro-
tates as the cam rotates but the be Ilcrank cannot operate the
intermediate pawl release lever (Fig. 61). Thus, the pawl
release lever is not operated and the escapement pawl remains
in the rack.
< l - Carriage Motion
Figure 61. Margin Control Bellcrank Operation
29
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