Carrier Return Mechanism - IBM Selectric Reference Manual

FIGURE 201.
Escapement Rack
Move Front to Rear
For Adj ustment
Intermediate Lever Adjustment (Late Level)
The rear portion of the intermediate lever is supplied
with the same amount of motion from the hexagon head-
ed screw on the be Ilcrank regardless of any change in
the front to rear position of the intermediate lever.
Therefore; the di fference in throw to the backspace rack
is achieved, when changing the front to rear position of
the intermediate lever, by increasing or decreasing the
leverage or distance between the pivot point of the in-
termediate lever and the backspace rack. Moving the
intermediate lever to the rear wi II increase the back-
space rack moti on.
During a powered backspace operation the carrier de-
velops enough momentum (allowing the escapement pawl
to properly overthrow and drop into the preceding rack
tooth) for a positive operation.
Too much motion to the backspace rack will cause
double backspacing. Check the operation at both ends
of the carriage so as to include the variation in the
mainspring tension.
CAUTION: The rest position of the backspace rack
shou Id be checked and readj usted, if necessary, after
any change in the front to rear position of the inter-
mediate lever.
NOTE: On 11 inch machines below serial number
Backspace
Intermediate
Lever
'- - )', '-
/-fi~il!V
\
_005"
to
'0I0'~
FIGURE 202. Intermediate Lever (Early Level)
2-68
4012015, the contour or rise to the spacebar backspace
operational cam is slightly different than those found
on later level machines. This cam provided much less
momentum to the carrier, therefore the backspace rack
required more moti on in order to produce a positive
backspace operation. Adjust this early level backspace
mechanism as follows: With the backspace cam man-
ua Ily operated to the high point, the escapement pawl
must drop into the preceding rack tooth and overthrow by
.005" to .010" (Fig. 202). Obtain this condition by
adjusting the intermediate lever forward or back in its
elongated mounting hole.
CARRIER RETURN MECHANISM
Be sure that the print escapement and operational control ad-
justments are correct before attempting the carrier return ad-
justments.
1. Carrier Return Latch Height (11 inch, machine) - With
the carrier return/index cam at rest, adjust the carrier
return latch height by the adjusting screw on the back-
plate (Fig. 203) so that the latch wi II pass under the
cam follower by .001" to .010" when it is released to
the rear.
Adjusting Screw
FIGURE 203. Carrier Return Latch Height Adjustment
(11 Inch Machine)
The latch height adjustment insures maximum throw for
the latch and that it wi II move under the cam follower
freely.
CAUTION: Any change in the carrier return latch
height directly affects the front to rear position of the
latch (with respect to the cam follower) when the ma-
chine is at rest. See adjustment #4 in the Operational
Control section.
NOTE: On long carriage machines the carrier return
latch height cannot be obtai ned unti I after the correct
pawl clearance and clutch latch overthrow adjustment
is obtained.
1.1 Carrier Return Latch Height Late Style
{II
Inch Machine}
With the carrier return cam at rest, adjust the carrier re-
turn latch height by the adjusting screw on the carrier
return adjusting plate so that the latch will pass under
the cam follower by .003" to .015" (Fig. 203.1).