IBM Selectric I/O Manual Of Instruction page 11

Carrier Support - Early
The front edge of the escapement rack serves as a rail on which
the rear of the carrier rides (Fig. 9). The escapement rack
is located on the powerframe just to the rear of the carrier. A
square block attached to the rear of the carrier sl ides along the
escapement rack. A simi lar block beneath the escapement rack
prevents upward movement of the carrier. The mounting stud
forthe upper block has an eccentric shoulder to provide an ad-
justment for the up and down play at the rear of the carrier.
Escapement Rack
FIGURE 9. Rear Carrier Support (Early)
Carrier Support - Late
The late carrier support (Fig. 10) differs from the early style
iin that the upper shoe fits loosely on its eccentric mounting
stud and is spring loaded against the top surface of the es-
capement rack. This spring load, provided by a leaf spring,
removes the play between the lower shoe and the bottom of
the escapement rack thereby eliminating any vertical play of
the rear of the carrier during a print operation. The bottom
~hoe
is a nylatron block mounted to a plate that is fastened
to the rectr of the carrier by the same stud that mounts the up-
per shoe. A stud, riveted to the plate, anchors the left end
of the leaf spring. The right end of the spring presses against
the underside of the escapement bracket (Fig. 10).
FIGURE 10. Rear Carrier Support (late)
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Rocker
The rocker is a pivoting platform located within the rear por-
tion of the carrier (Fig. 11). Its purpose is to carry the type-
head to and from the platen for the print operation. Compon-
ents involved in the type head positioning and aligning opera-
tions are also contained within the rocker. The rocker pivots
on the rocker shaft at the rear of the carrier. Two bushings,
pressed into the rocker, pivot on the shaft and act as the
bearing surface for the rocker. A C-clip on the right side of
the rocker shaft prevents si de play in the rocker. A stee I
thrust washer at the left of the rocker acts as a latera I bearing
surface for the rocker.
Attached solidly to the top of the rocker platform is the yoke
(Fig. 11). The yoke has two arms that extend up to provide
a pivot mount for the ti It ring. Mounted at the top of the ti It
ri ng is the upper ba
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socket to whi ch the type head is attached.
As the rocker pivots up in front, the yoke moves the ti It ring
and the typehead toward the platen.
Upper Ball Socket
Tilt Ring
FIGURE 11. Rocker Assembly (Gear Tilt)
Typehead
Before printing can occur, the desired character must be in po-
sition to strike the paper. The surface of the typehead con-
tains four bands of raised characters with twenty-two in each
band (Figs. 12 and 13). Each band has eleven lower case
characters in the hemisphere facing toward the platen and
eleven upper case characters in the hemisphere facing away'
from the platen.
At rest, the position of the typehead is such that the middle
character of the upper band is in position to strike the platen.
This is the home position. If any character other than the