IBM Selectric I/O Manual Of Instruction page 98

The empty spool rotates slightly farther causi ng the reverse
trigger to contact and actuate the reverse lever which pivots
just below the ratchet (Fig. 196). The reverse lever is con-
nected, by means of a flat link, to an arm of the reverse
yoke beneath the ribbon feed plate. The yoke is pivoted by
operati on of the reverse lever. A stud on the yoke at the
rear of the pivot point extends up through the feed plate in-
to a slot in the reverse interposer. Movement of the yoke po-
sitions the front of the reverse interposer left or right depend-
ing upon which ribbon spool is being emptied (Fig. 197).
Ribbon Reverse
Interposer
Ribbon Feed Detent
Lever
FIGURE 196. Ribbon Reverse Mechanism - Rest Position
Pin Projects Through
Slot In Interposer
FIGURE 197. Ribbon Reverse Mechanism - Active Position
Positioning the reverse interposer does two things. A hook at
the front of the interposer hooks around a lug on the ribbon
feed detent lever (Fig. 198). The interposer lever, mounted
on the interposer, is posi ti oned into the path of the ri bbon
78
feed pawl. The next operati on of the ri bbon feed cam causes
the feed pawl to drive the reverse interposer to the rear. The
hook at the front of the interposer pulls the lug of the detent
lever to the rear causing the detent lever to pivot to the op-
posite position. Movement of the detent lever disengages the
detent pawl at the full spool and allows the pawl to engage
the ratchet at the empty spool. As the feed pawl restores, its
spring pivots it over into engagement with the opposite rat-
chet.
FIGURE 198. Ribbon Reverse Interposer And Lever
The purpose of the interposer lever is to prevent the motion of
the ribbon reverse interposer from being choked off during a
reversing operation by the ribbon feed pawl, if the feed pawl
shou Id become trapped between the ribbon feed ratchet and
the interposer lever.
Stenci I Lockout
When the ribbon lift lever is placed in its no lift or stenci I
position, a latch called the ribbon feed latch is allowed to
interrupt and hold the ribbon feed cam follower from follow-
ing the ribbon feed cam back to its low point tFig. 199).
This causes the ribbon feed cam follower to become crippled
thereby locking out the ribbon feed operation. The ribbon
feed latch mounts on a stud on the ribbon feed follower
mounting bracket and is spring loaded into its active position
by a small hairpin spring. The ribbon lift lever controls the
position of the latch. When it is pushed to the right into
the stencil position, it allows the latch to rotate against the
top surface of a lug on the cam follower. As the follower is
operated forward by the feed cam, the latch hooks behind
the lug on the follower and prevents the follower from follow-
ing the cam back to its low point. This cripples the feed
operation because the cam follower no longer receives
enough motion to operate the ribbon feed pawl effectively.
Pushing the ribbon lift lever to the left (out of the stenci I
position) cams the latch into its inactive position, thereby
releasing the follower so that it can be operated by the feed
cam.