Indexing - IBM Selectric I/O Manual Of Instruction

CONTACT
FIGURE 146. Carrier-Return Interlock Contact
The interlock contact is operated by the carrier return clutch
latch. An extension has been added to the latch for this pur-
pose (Fig. 147).
Carrier-Return Latch
Extension
FIGURE 147. Carrier-Return Clutch Latch
When the latch is in its rest position, the contact is in its
normal position. As the latch is operated, the extension
moves down, transferring the contact. In the latched posi-
ti on the extension holds the contact transferred (Fig. 148).
When the carrier return operation is completed, the latch un-
latches and the contact returns to norma I (Fig. 149).
Keeper
Latch
Interlock Contact
FIGURE 148. Carrier-Return Interlock When Latched
59
FIGURE 149. Carrier-Return Interlock When Unlatched
INDEXING
Indexing
The indexing mechanism operates to line space the paper ver-
tically. An indexing operation can be obtained by depress-
ing either the carrier return keylever or the special indexing
keylever. Depressing the carrier return keylever a Iso causes
the carrier to move to the left margin; whereas depressing the
index keylever (not used on some printers) causes a line space
operation only.
The index selector lever, located to the rear of the right end
of the platen, may be positi oned so that the mechanism wi II
space either one or two spaces during each operation. With
the lever forward, sing Ie line spacing will occur. Double
spacing wi II take place if the lever is to the rear.
Indexing is achieved by a pawl that engages and rotates a
ratchet at the right end of the platen. The ratchet is locked
to the platen so that the platen is also rotated. Two styles of
indexing mechanisms have been produced.
Early Style Indexing
The index pawl pivots on a bellcrank called the index pawl
carrier (Fig. 150). The carrier pivots just behind the platen
on the right hand carriage plate. A small extension spring
at the top of the index pawl spring-loads the pawL toward
the platen ratchet. The index pawl is held clear of the rat-
chet in the rest position by a lug on the upper index stop lo-
cated just to the rear of the pawl (Fig. 150). As the pawl
carri er is operated down by the I ink attached at the rear, the
Index Pawl
FIGURE 150. Index Pawl Rest Position