Film Frame Transport And Spreading - Polaroid Joshua Vision Service Manual

Exposure ends and the blades are closed when the sum of the visible and IR integrator values equals the
selected total. (If this selected total has not been reached when the strobe is quenched, the blades stay open
and the ambient integrator is turned back on (enabled) until additional ambient completes the exposure or a
40 ms Timeout is reached.
To end the exposure and close the blades as rapidly as possible, Solenoid 1 is energized and the Inertia is
left behind. A weak Inertia Coupling Spring then resets the inertia to its original position, after the shutter
has closed.
Note:
Film Frame Transport and Spreading (Figures 1-20 and 1-21)
When exposure of a film frame has been completed, the drive motor starts in the forward direction, turning
the Timing Gear. This causes: the Darkslide/End of Cycle switch (DKEC) to close; the picture Counter
Wheel to index one count; and the exposed frame to be pulled into a set of two Feed Rolls by a Pick
Assembly.
These rolls have rubber tires (O rings) which contact the frame along its edges, drive it through the chute
and into the Spread System Rolls (Figure 1-20). Just before the frame enters the Spread Rolls, it passes
over opposing, slightly projecting molded surfaces on the bottom of the Film Box and part of the Spread
Roll Assembly (Figure 1-21). These molded features help position the reagent more evenly in the picture area
before actual spreading occurs.
At the same time the frame enters the Feed Rolls, a mechanical Film Shade (similar in function to the frog's
tongue in other Polaroid cameras) is automatically positioned over the first 1.9 cm (.75") of the picture
Viewing Window. The Film Shade prevents light-piping fogging of undeveloped film through its
transparent mylar coating.
The frame now enters the Spread Rolls which break open the reagent pod and spread the reagent. A second
chamber Pick (See Figure 2-27 on Page 2-21) in the Door catches the end of the processed frame from the
mating point (nip) of the Spread Rolls. This is to ensure that the processed frame is pulled clear of the Spread
Rolls and is positively carried into the picture Storage Chamber, where it will not interfere with the next frame
to be spread.
The film Chute, Chamber and associated transport mechanisms are designed to permit trouble-free insertion
of additional film frames, either from the Chute or through the storage chamber Door, until 10 frames and a
darkslide are in the storage chamber. At that point, a Full-Chamber Switch is closed, inhibiting further
picture taking.
For a simplified pictorial presentation of these steps,
see the Exposure section of the Polaroid Joshua
Sequence of Operations chart at the beginning of the
Theory of Operation section. (See Page 2-4)
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