IBM Selectric I/O Manual Of Instruction page 68

The spacebar contains a metal stem pressed into the body of
the spacebar (at the center). The stem extends down into a
slot in the spacebar return spring. The spacebar return spring
is a flat
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leaf-type spring that is mounted to the front key-
lever guide comb support by two screws and performs the
function of restoring the spacebar to its rest position. This
spring a Iso guides the bottom of the spacebar stem to prevent
tipping of the spacebar forward or back. Additional support
is provided by a lever that extends forward from the spacebar
shaft. A guide stud on the lever fits through an elongated
hole in the spacebar stem.
Attached to the right end of the spacebar shaft is the space-
bar operating arm whi ch extends to the rear through a slot
tn the front keylever guide comb (Fig. 130). When the
spacebar is depressed the operating arm is raised. The arm
contains a slot in the end that fits into a fork in the forward
end of an intermediate lever called the spacebar lever. When
the spacebar is depressed
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the rear of the spacebar lever and
the attached spacebar lever pawl are lowered. The spacebar
lever pawl then pushes down on the spacebar interposer caus-
ing the interposer to unlatch from the keylever pawl guide
bracket. The interposer snaps to the rear
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releases the
spacebar/backspace/tabu lating cam
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and pushes the spacebar
operati ona I latch under the cam follower.
The spacebar latch is mounted to the spacebar lat-ch lever by
a ball shouldered rivet to permit free movement of the latch
(Fig. 131). The spacebar latch lever is mounted on a pivot
pin on the operational latch bracket assembly which is at-
tached to the rear of the powerframe just in front of the
mainspring.
Adjusting Screw
FIGURE 131. Spacebar Latch Operation
When the spacebar latch is operated down by the cam fol-
lower
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the spacebar latch lever pivots about its pivot pin.
An adjusting screw on the latch lever contacts the trigger
lever causing the trigger lever to rotate about its pivot pin
(Fig. 131). This causes the triggers on the trigger lever to
rotate the escapement torque in the same manner as it does
duri ng a pri nt escapemen t operati on. Thus the escapemen t
and backspace pawls are removed from their racks and an es-
capement operati on takes place.
Spacebar Stops
Two styles of final stops have been produced and used on the
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early style spacebar mechanism. Both styles attach to the
middle of the keylever guard at the front of the machine and
function by blocking the downward travel of the spacebar
stem (Fig. 130).
Upward travel of the spacebar is limited by the spacebar
stem. A step in the stem contacts the bottom of the spacebar
shaft (Fig. 133). A vinyl sleeve on the stem cushions the
spacebar in the rest position to prevent noise.
Repeat - Optional
The downward travel of the spacebar is limited at two posi-
tions. The first limit allows a single operation only. Further
depression of the spacebar causes the first limit to yield to
permit a repeat operati on. A final limit prevehts further de-
pression.
An extensi on spri ng at the front of the spacebar lever acts as
a first limit for the mechanism (Fig. 132). The lower end of
the spring is formed into a long hook. The hook is connected
into an elongated slot in the ~epeat spring stud. As the
spacebar is depressed
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the front of the spacebar lever and the
repeat spring are raised. The spacebar reaches the first limit
when the repeat spring contacts the top of the elongated slot
in the repeat spring stud. Further depression of the spacebar
causes the repeat spring to yield and allow the spacebar to
move into the repeat positi on.
Spacebar
Operating Arm
Repeat Spring Stud
FIGURE 132. Spacebar Repeat Stop -
New Style (Optional)
Spacebar Lever Mechanism - Late Level
The late level spacebar mechanism is basically the same as
the early level. The main difference is in the spacebar stem.
A stabilizing link has been attached to the bottom of the stem
by a shou Idered rivet (Fig. 133). The rear porti on of the
link mounts on and pivots about an adjustable guide stud.
This stud is fastened to a support on the front keylever bearing
support by two screws. The stabilizing link controls the bot-
tom of the spacebar stem to prevent the spacebar from tipping
forward or back.
The spacebar restoring action is supplied by an extension
spring that is attached to the spacebar operating arm and
anchored to one of three holes in the carrier return/backspace
repeat bail. In addition, the spacebar guide stud and the
final stop as found on the early level mechanism has been
eliminated from the late level spacebar mechanism.