Spacebar Mechanism (Print Escapement) - IBM Selectric I/O Manual Of Instruction

If the spacebar interposer is tripped, it wi II move to the rear
slightly unti I it contacts the lockout cam extension. The in-
terposer will remain tripped against the lockout cam until
the print cycle has been completed. As the filter shaft ap-
proaches the rest position, the lockout cam is forced back to
the left by the escapement cam. The spacebar interposer is
then released to the rear for a spacebar operation.
Spacebar Lockout - Late Style
The spacebar interlock mechanism is mounted within the op-
erational control bracket just below the filter shaft. It con-
sists of a bracket, an interlock interposer (which acts as a
cam follower) and an interlock cam mounted on the fi Iter
shaft (Fig. 135).
When the filter shaft is in its rest position the upper extension
of the interlock interposer is resting on the high point of one
of the lobes on the interlock cam. This allows the horizontal
lug on the lower extension of the interlock interposer to just
clear the adjustable stop on the spacebar interposer as it op-
erates to the rear duri ng a spacebar operati on (Fig. 135).
Spacebar Interlock Cam
Adjustable Stop
FIGURE 135. Spacebar Lockout - (Late Style)
Whenever a print operatio!'" occurs, the filter shaft and inter-
lock cam will begin to turn causing the rear portion of the in-
terlock interposer to rise into the operating path of the space-
bar interposer. If the spacebar interposer were then released
the interlock interposer wou Id interrupt and store the rear-
ward travel of the spacebar interposer unti I the fi Iter shaft
completes its cycle. At this time the spacebar interposer
would be released to finish its rearward travel and the space-
bar operation wou Id complete. Note that the interlock inter-
poser is spring loaded into its active position and powered to
its rest position. This is to prevent breakage should both the
spacebar and print operation be operated simultaneously.
Spacebar Mechanism (Print Escapement - 835 Printer)
The spacebar mechan ism of the 835 Printer uses print escape-
ment to operate the trigger assembly. The spacebar operation
now regu ires the same amount of time as a character operation.
Located on the left end of the spacebar shaft is the spacebar
operating arm and a lug to provide for a spacebar tension
spring (Fig. 135.1). Depression of the spacebar, rotates the
spacebar shaft and moves the operating arm downward. A
pin on the spacebar operating arm fits in a slot on the space-
bar keylever and as the operating arm rotates downward, the
keylever is depressed (Fig. 135.1). The keylever pawl con-
tacts the spacebar interposer and forces it downward in front
of the filter shaft. At this point the cycle clutch is tripped
Spacebar
Spacebar Operating
Spring
• FIGURE 135.1 Spacebar Keylever Mechanism
•
54
and the filter shaft drives the spacebar interposer forward. An
extension on the front of the interposer moves a lug on the
no-print vane, rotating the no-print bellcrank and pulling on
the no-print link (Fig. 135.2). Forward movement of the link
Spacebar Interposer
FIGURE 135.2 Spacebar Interposer