Tilt Mechanism - IBM Selectric I/O Manual Of Instruction

Platen
Upper Case
Hemisphere
Lower Case Hemisphere
Type Head
FIGURE 12. Type Head and Platen - Top View
home position is desired, the head must be ti Ited up and/or
rotated in either direction unti I the desired character is in
the printing position. Any lower case character may be
reached by rotating the typehead up to five positions in either
di recti on and ti It'ing the headi as much as three bands from the
rest position. The typehead always rotates back to the home
or rest position after a character has been typed. If an upper
case character is desired, the head must be rotated counter-
clockwise an additional 180
0
so that the upper case hemis-
phere of the typehead is toward the platen. The single-unit
typehead has the advantage over conventiona I typebars of be-
ing relatively inexpensive and easily detached from the print
mechanism. This enables the operator to chcmge quickly and
easi Iy from one type style to another merely by replacing the
typehead.
Lower Case Home
Spring Clip
Platen
Type Head
FIGURE
13.
Type Head and Platen - Side View
The type head fits a round a post ca lied the upper ba II socket
at the top of the rocker assemb I y and is he Id in p lace by a
spring clip. The spring clip is located on top of the typehead
and fits into a groove in the top of the post (Fig.
14).
A con-
ves disc, covers the spring c Ii p except for two ears (Fig. 12
and 13). The ears of the spring clip are used in removing and
insta lIing the head. By pressing the two ears together the
spring c lip is disengaged from the groove in the mounting post
a 1I0wi ng the head to be s lipped up and off.
5
Type Head
Type Head
Retaining Clip
FIGURE
14.
Type Head Mounting
The typehead may be installed by pressing the ears of the
spring clip together and slipping the head into place. The
typehead is keyed to the upper ball socket by a pin so that it
can be installed in one position only (Fig.
14).
The head
must be rotated as it is insta lied unti I it drops into position on
the pin. The spring c lip is then released to lock the head in
place. When the mechanism is at rest, the typehead is always
in the home position. When the shift mechanism is in the low -
er case position, the ears of the head clip are toward the front
of the machine.
TILT MECHANISM
Tilt Operation
The purpose of the ti It mechanism is to raise the rear of the
typehead to the desi red character band so that a character in
that band may be brought to the printing point.
The upper ba II socket is attached to a platform-like part ca lied
the ti It ring. The ti It ring pivots on two pins between yoke
arms that fit up inside the hollow of the typehead. The yoke
assembly is fastened to the rocker to complete the typehead
mounting (Fig. 11).
The ti It ring is located at about the center of the typehead.
As the ti It ring pivots on its pins, it causes the typeheadto
ti It. Because the typehead rests with the upper band in the
print position, all tilt operations are upward from the rest po-
sition.
Early Style (Gear Ti It)
Movement of the ti It ring is accomplished by the operation of
two beveled gear sectors located directly beneath the tilt ring
(Fig. 15). One sector forms part of the tilt ring, while the
other is a part of the ti It sector tube. Rotati'on of the tilt sec-
tor tube causes the ti It ring and typehead to be tilted.
The tilt sector tube operates through the yoke and extends be-
low the rocker. A pulley called the tilt sector pulley is at-
tached to the bottom of the tube. The pu Iley is he Id to the
tube by a set screw that presses a sma II T -shaped block agai nst
a flat surface on the tube. The pulley is held in a clockwise
di recti on (looki ng from the top) by an extensi on spri ng. A
sma II stee I tape enci rc les the pu lIey and has one end attached
to it. When the tape is pulled, it causes counterclockwise
rotati on of the ti
It
tube and an accompanyi ng ti It of the type-
head. When the pu lion the tape is re laxed, the ti It pu lIey