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ACTUATOR. CARR 'AGe
RETRACTED
M:T'UATOIt
HClUSING
PAlfrIA" HEAD
COM .... £JlllENT
SHOWN
ACTUATOR. CAM'AGE
I
EXTEND ..
,
...
Fiqure 3-8. Actuator Assembly Elements
The actuator contains a stop mechanism to
limit extremes in forward and reverse move-
ment.
The stop assembly is a rubber cylin-
der sandwiched between two metal plates. If
the carriage moves too far toward the disk
pack, the stop rod heads contact the plate
on the magnet-side of the rubber cylinder.
If the carriage is retracted far enough
away from the disk pack, the rear of the
head/arm receiver contacts the stop
assa~
bly stud protruding through the stop plate.
Head Loading
The read/write heads must be loaded to the
disk surfaces before exchanging data with
the controller.
The heads must be removed
(unloaded) from this position and driven
clear of the disk pack either when power is
removed from the unit or when the disk pack
velocity falls below about 2700 rpm.
The
3-14
actuator components invotved in these oper-
ations are identified in Figure 3-9.
Head loading amounts to allowing spring
pressure of the floating arm (part of head/
arm assembly) to move the aerodynamically
shaped head face toward the related disk
surface.
When the cushion of air that exists
on the surface of the spinning disk is en-
countered, it resists any further approach
by the head.
Spring pressure is designed to
just equal the opposing cushion pressure
(function of disk pack rpm) at the required
height.
As a result, the head flies.
How-
ever, if the spring pressure exceeds the
cushion pressure (as would happen if the
disk pack lost enough speed),
t~e
head stops
flying and contacts the disk surface.
This
could cause damage to the head as well as
the disk surface.
83318200
A
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