IBM 727, Руководство по инструкции

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When this solenoid is energized, the horizontal shaft is rotated counterclockwise
(as viewed from the left side) causing the arm and fork at (4) to push the capstan
mechanism to the rear. Also attached to the solenoid armature is a dash-pot arm
to pull the plunger in a dash pot, cushioning the action of the capstans. Inside the
dash pot is a coil spring that is com pressed when the capstans are retracted. This
spring is the source of power to extend the capstans.
The horizontal capstan shaft is driven from the solenoid through a torsion spring.
When the solenoid is unlatched, the dash-pot spring turns the horizontal shaft, and,
through two torsion springs, extends the capstans. Located on the horizontal shaft
are two capstan "out" microswitches and one capstan "in" m icroswitch. They indi­
cate electrically the positions of the capstans.
The solenoid has a latch to hold the solenoid plunger down after it is pulled
down. A latch magnet is provided to release the latch and the plunger when desired.
The pulleys driving the capstans remain stationary; the shaft is merely pushed in
and out.
A definite sequence of operation is necessary when extending the capstans under
electrical control. The retracting solenoid must first be energized to remove the
pressure from the latch pin. The latch magnet can then retract the latch pin. While
the pin is being held out of the way, power is removed from the retracting solenoid
allowing the capstans to extend. Finally, the latch magnet is de-energized.
4.10 HEAD-RAISING MECHANISM
The mechanism that raises the upper portion of the head assembly is directly
behind the upper front plate. It consists of a screw shaft, driven from a friction
clutch and drive chain by a small take-up m otor. The take-up motor is mounted
above and between the two clutch shafts.
When the motor is operated in one direction, the screw shaft turns in a clock ­
wise direction causing the upper head assembly to move upward. When the motor is
operated in the opposite direction, the shaft turns counterclockwise and lowers the
assembly. M icroswitches are operated at both limits of travel to indicate the posi­
tion of the head cover assembly.
In addition to operating the screw shaft, the motor is geared to each of the brake
clutch housings so that, when the head is being raised, the left stop clutch housing is
rotated in a counterclockwise direction and the right stop clutch housing is rotated in
a clockwise direction. The brake clutches are energized at this time and the reels
are driven in the above mentioned direction. This causes tape to be pulled from both
columns. The opposite occurs when the head assembly is lowered and tape is lowered
into the columns.
4.11 REEL DOOR INTERLOCK
Located in the lower left-hand corner of the reel door is an interlock switch that
is closed when the door is closed. When the door is open, operation of the reel drive
motors is prevented. For convenience of the customer engineer, this switch can be
closed with the door open by pulling out the operating plunger.
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