Print Mechanism (Late Style) - IBM Selectric I/O Manual Of Instruction

Platen Ecc.
Retaining Plate
Platen Latch Pivot
Copy Control Eccentric
FIGURE 105. Copy Control Mechanism
Copy Control
The purpose of the copy control mechanism is to position the
platen forward or back for different thicknesses of typing
material. Positioning the platen maintains the correct re-
lationship between the anvi I and the point of impact of the
type head with the paper.
The copy control is operated by means of the copy control
lever located at the left end of the carriage (Fig. 105). The
lever is attached to the copy control shaft that extends out
through the sides of the powerframe. An eccentri c collar at
each end of the shaft operates between adjusting parts at-
tached to the carriage ends. When the lever is moved to the
rear, the shaft rotates causi ng the eccentri c collars to con-
tact the platen eccentric retaining plates clnd force the car-
riage ends to the rear. The platen and entire paper feed
mechanism move with the carriage. When the copy control
lever is pulled forward, the eccentric coll(]rs contact the
platen adjusting plates and force the carriCige forward into
the normal position.
The copy control lever can be set in five different positions.
A spring detent attached to the powerframe acts against a
knob on the copy control lever to hold it in place.
PRINT MECHANISM - LATE STYLE
The new style print mechanism contains an operator impression
control lever which permits the operator to regulate the im-
pression for any appl ication she may type. The operator may
change the over-all impression of the typehead by merely
positioning the impression control lever to one of five settings.
In addition, the new style print mechanism is equipped with
an automatic velocity selection mechanism. The purpose of
this mechanism is to provide a lighter impression for the pe-
riods, commas, colon, semi-colon, quotation mark, apos-
trophe, hyphen, and underscore; regardless of where the im-
pression control lever may be set.
Before going into any detai I on the impression control mecha-
nism it is necessary to first understand how the automatic ve-
locity selection mechanism operates since both mechanisms
are directly related.
•
Automatic Velocity Selection - (UDual CamU)
The printing operation of all the upper and lower case charac-
ters in positions 32, 36, 38, 39, and 42 produce a lighter im-
pression on the typed copy than all the other positions. The
reason
'~or
this is to improve the general appearance of the
typed copy by producing a more uniform impression between
all characters, lorge or small. This is accomplished by using
a print cam that has two different camming surfaces (Fig.
105.1) •
FIGURE 105.1 Print Cam (dual velocity)
The low and high points of both camming surfaces are identical.
The only difference is in the contour (profile) between their
low and high points. The contour of one camming surface pro-
vides the type head with a lower impact velocity than the
other. Thus, a I ighter impression is produced when this cam·-
ming surface is used. The difference in type head velocities
produced by the two camming surfaces remains proportional
regardless of the impression control lever setting.
A selection mechanism positions the print cam follower roller
under the proper camming surface of the dual velocity print
cam whenever a character is selected at the keyboard. The
print cam follower assembl y (Fig. 105.2) is mounted on a
pivot pin located in the right side of the carrier below and
to the rear of the print cam (just as it is in the old style print
mechanism). The print cam follower roller mounts on a pin
on the print cam follower and is free to sl ide left or right on
this pin.
High Velocity Lobe
Low Velocity Lobe
Follower
•
FIGURE 105.2 Print Cam Follower Assembly
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