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'Brush
Mid-Cycle'
Link
Microswitch
Cam
Figure 1-15. Disk Cleaning Brushes Linkage Mechanism
[07475)
Brush Motor
The brush motor is a synchronous motor: the output
spindle rotates at approximately 2 rpm. Because the
5444 can be operated from 50 Hz and 60 Hz power
supplies, different brush motors are available (see
Appendix B).
ACTUATOR
• The actuator positions the read/write heads at track
addresses defined by the using system.
• The carriage holds and positions the read/write heads
over the disks.
• The access mechanism moves the carriage.
5444 (<30100) FETMM
(5/70)
1-9
• The detent mechanism stops the carriage.
• Inner and outer limit switches restrict carriage
movement.
The actuator (Figure 1-16) accurately positions the four
read/write heads at the track address defined by the
using system. This positioning is carried out within a
specified time, the external control signals being
provided by the using system.
Carriage
• The carriage moves on linear ball slides within the
actuator frame carrying the read/write heads over the
disks.
• The read/write heads are in a loaded condition as they
move out.
The carriage is mounted within the actuator frame and
runs on linear ball slides. Read/write heads on support
arms are fitted into slots in the carriage. As the carriage
moves along the actuator frame, the read/write heads
move across the disk surfaces. Switches attached to the
actuator frame prevent the carriage from hitting its
limits of travel.
Four head load spring shafts (Figure 1-17) on the
carriage are operated by a geared linkage mechanism
coupling all four shafts together to load simultaneously.
The linkage is operated by a flexible head load cable and
a head load lever attached to shaft number 02. The head
load mechanism has a mechanical knock-off (trip arm
and trip) to unload the heads if the carriage is retracted
off the disks with the read/write heads still loaded. The
head load mechanism is described later in this chapter.
Actuator Mechanism
• Carriage movement is obtained from a rotating
leadscrew.
• The leadscrew drives a follower wheel mounted in the
carriage.
• Motive power for leadscrew rotation is obtained from
a layshaft via a drive tire and flexible drive disk.
• One of the two clutches holds the flexible disk against
the drive tire to give the required direction of carriage
movement.
Actuator Assembly
Frame
Figure 1-16. Actuator Assembly
[07476)
The carriage is driven long the actuator frame
by
a
leadscrew acting on a spring-loaded follower wheel and
rollers attached to the carriage (Figure 1-18). The
leadscrew is held in bearings at each end of the actuator
frame and is rotated from the layshaft (see Figure 1-20).
The layshaft is driven from the drive motor via a drive
belt and rotates continuously while the machine is in
operation. A flexible stainless steel drive disk is attached
to the end of the leadscrew (Figure 1-19).
One of two clutch pads holds the drive disk against the
rotating drive tire. The upper (forward) clutch holds the
disk against the upper driving surface of the tire to move
Carriage
Slides
Read/Write
Head Assembly
(Downward Facing)
Read/Write
Head Assembly
(Upward Facing)
Carriage Photocell
Assembly
the carriage towards the center of the recording disks.
The lower (reverse) clutch holds the disk against the
lower driving surface to move the carriage away from the
center of the recording disks.
A pressure pad fixed to the end of each clutch
armature prevents wear on the drive disk when the disk
is held against the drive tire. When a clutch is energized,
the pressure pad moves towards the drive tire, forcing
the flexible disk against the tire driving surface. When
the clutch is de-energized, a return spring returns the
armature holding the pressure pad to its stop position.
The leadscrew has a pitch of 0.1 in. (2,54 mm). One
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