IBM Selectric I/O Manual Of Instruction page 96

hold the cartridge down to prevent vibration. After the rib-
bon is installed, the load lever is moved back to the left to
allow the ribbon lift guide to restore to its normal position
ready for a typi ng operati on •
Ribbon Lift
The ribbon lift mechanism consists of a cam, cam follower,
control mechanism, and the ribbon lift guide assembly (Fig.
192) •
The mechanism is mounted to the carrier assembly and is
transported by the carrier along with the typehead. The rib-
bon lift cam is a sing Ie lobed cam set-screwed to the left end
of the print sleeve. The cam has a punch mark on the right
side that must line up with the print sleeve key-away to in-
sure that the cam is not out of time with the print operati on.
Care must be taken if the cam is replaced, to insure that it
is not installed in a reversed position.
The cam makes one complete revolution each time a cycle
operation occurs. The ribbon lift cam follower pivots on the
carrier casting above and to the rear of the cam (Fig.
192).
Each operation of the cam raises the cam follower. The cam
follower contains a long slot. In the slot is the end of the
ribbon lift control link. The ribbon lift guide assembly rests
directly above the control link. As the cam follower is
raised, the control link forces up on the ribbon lift guide as-
sembly. The guide assembly pivots on the carrier casting at
the front causing the ribbon to be raised at the rear. A flat
link from each side of the ribbon lift guide attaches to two
pins at the front of the carrier to maintain the ribbon lift
guide in a vertical position.
The height to which the ribbon wi II be raised is determined
by the position of the ribbon lift control link in the slot of
the cam follower. When the I ink is in the extreme rear of
the slot, very little motion is obtained from the cam follower;
consequently, the ribbon lift guide is not raised at all. This
is called the stencil position. It is so called because the
ribbon is not used in typing stencils.
As the ribbon lift control link is moved toward the front in
the slot, more and more motion is obtained from the cam fol-
lower. The link is also moved nearer the pivot point of the
ribbon lift guide assembly so that the motion obtained from
the follower is more effective in raising the ribbon. The
nearer the front the link is moved, the higher the ribbon will
be raised.
In addition to the stenci
1
position there are three ribbon lift
positions which may be selected by the operator. The ribbon
lift control link is attached to the ribbon lift control lever
pivoted under the front of the carrier casting (Fig.
192).
The
control lever is spring-loaded to the rear against a stud on
the ribbon lift lever. The ribbon lift lever has a button lo-
cated just to the left of the carrier pointer. Moving the but-
ton to the left causes the stud on the lever to force the ribbon
lift control lever and link toward the front. The stud of the
ribbon lift lever seats into notches in the control lever to
maintain its position unti
1
changed by the operator.
The extreme right hand position of the button is the stencil
position where no ribbon lift is avai lable. The next position
to the left is the low lift position used for typing on the top
half of the ribbon. The third position allowll typing in the
middle of a single colored ribbon to get maximum life from
the ribbon. The extreme left position of the button is the
high lift position and is used for typing on the bottom half
of the ri bbon •
The ribbon lift guide assembly is spring loaded into the rest
position to insure that it will restore rapidly and to prevent
overthrow of the ribbon due to the momentum of the lift
mechanism.
Ri bbon Feed and Reverse
1. Ribbon Feed
The ribbon feed and reverse mechanism is a compact unit
mounted at the top of the carrier just in front of the typehead.
The mechanism is detachable as a unit for repair or replace-
ment purposes.
Each ribbon spool of the ribbon cartridge unit fits over the
core of a nylon ribbon feed ratchet (Fig.
193).
Rotation of
a ratchet causes the spool to turn and wind up the ribbon.
The ratchets are operated by a pawl that moves front to rear
between them to force the ratchet teeth to the rear.
The position of the feed pawl determines which ratchet is fed
as the pawl moves to the rear. The feed pawl pivots on a pin
beneath the ribbon feed plate and extends up through a hole
in the plate. The mounting of the pawl permits left to right
as well as front to rear movement. An extensi on spring at-
tached to the pawl restores the pawl to the rest position each
time it operates (Fig.
193).
The spring also holds the pawl
left or right into engagement with the correct ribbon feed
ratchet depending upon the direction of pull of the spring.
The forward end of the spring is attached to a lever called
the ribbon feed detent lever. The detent lever pivots on the
ribbon feed plate.
Ribbon Feed Ratchet
Ribbon Feed Pawl __
I
~~ ~-~
(
\
/"
~~
( ~ ~
)) f
'g
) \ ~
\ // !J
" ___ ,::.1
~
76
"",,-~... ~'
Ribbon Feed Detent Lever
Ribbon Feed Detent
Pawl
FIGURE
193.
Ribbon Feed Mechanism - Top View