TM 11-6720-239-35
in the raised position and the tab at the top of the
(small) opening in the aperture wheel is posi-
lighting selector actuator assembly is against the
tioned directly in line with the lens and shutter.
left stop. In this position, only the larger aperture
The aperture opening used is determined by the
position of the lighting selector control.
openings are selected and the readout indicator
will be to the far left.
A spring loaded detent block is connected to the
actuator arm of the lighting selector control, and
rides the toothed ratchet of the aperture wheel.
ter is cocked by depressing shutter cocking lever
The openings in the aperture wheel are oriented
3. As the lever is depressed, the following actions
to the teeth on the ratchet.
pertinent to shutter cocking occurs:
The larger openings are slightly offset from the
(1) As shutter cocking lever 3 travels in a
crest of the tooth. When the detent block is in the
downward direction it pulls the cocking slide, and
raised position and cradled in the trough between
spring loaded opening blade, to the right.
teeth, the larger opening to the left of the top
(2) As the opening blade travels from left to
tooth is directly in line with the lens. As long as
right it carries the spring loaded closing blade
the detent block is in the raised position, only the
with it.
larger openings will be selected as the FILM
(3) When the latch pin on the opening blade
SPEED dial settings of the aperture wheel are
strikes the spring loaded blade latch, it travels up
changed.
the forward edge of the blade latch and forces the
The smaller openings in the aperture wheel are
blade latch down.
slightly offset from the trough between teeth.
(4) When the latch pin clears the shoulder of
When the detent block is in the lowered position,
the blade latch, the blade latch snaps back up lock-
and cradled in the trough between teeth, the
ing the latch pin, and opening and closing blades,
smaller opening to the left of the top tooth is
in the cocked position.
directly in line with the lens.
(5) As the blade latch snaps back up, it re-
The position of the detent block is shifted by the
leases spring loaded timing switch S2. As the
lighting selector control. When the lighting selec-
blade latch was being forced downward, it opened
tor control is in the extreme left (dull) position,
timing switch S2. When the blade latch snaps
the detent block is in the lowered position and the
backup, it closes timing switch S2.
tab at the top of the readout actuator assembly is
against the right stop. In this position, only the
cocked shutter is released when shutter release
smaller aperture openings are selected and the
button 2 is depressed. Shutter release button 2 is
lighting selector indicator will be to the far right.
connect ed to the shutter assembly by a cable as-
When the lighting selector control is in the ex-
sembly. When shutter release button 2 is de-
treme right (bright) position, the detent block is
Figure 1-2. Shutter cocking mechanism,
1-2
