| 摘要 |
A film cassette is disclosed wherein a film spool having a film roll coiled about it is rotated in an unwinding direction to advance a leading section of the film roll into and through a film passage slit to the outside of the cassette shell. The film spool includes a pair of annular constraining lips coaxially disposed on the spool core to space the outermost convolution of the film roll from an interior curved wall of the cassette shell. The leading section of the film roll is tapered asymetrically and is relatively short to allow it to protrude from between the constraining lips and into slight contact with the shell wall. When the film spool is initially rotated in the unwinding direction, the spool core is rotated relative to the constraining lips until there results a firm non-slipping relation between the outermost convolution and the lips, to thus cause the lips to be rotated thereafter with the spool core. The non-slipping relation imparts a beam strength to the leading section of the film roll which, when the film spool is rotated in the unwinding direction, combines with the asymetric design of the leading section to increase the likelihood that the leading section will feed into the film passage slit.
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