| 摘要 |
An Indicator device for use with a web of material having perforations therein of a first pitch along an edge incorporates a wheel having a plurality of teeth that have a pitch that is less than the pitch of the perforations in the web of material. A spring urges the wheel into contact with the web of material such that at least one tooth on the wheel engages a perforation on the web of material. As the web and the wheel move relative to each other when a tooth is aligned with a perforation, the movement of the web of material then rotates the wheel until the tooth disengages with the aligned perforation. When a tooth is not aligned with a perforation on the web, the wheel and its teeth slide on the web of material until a tooth is aligned with a perforation. The diameter of the wheel and the associated teeth translating into the pitch between the teeth can thus be much smaller than a wheel with teeth having the same pitch as the perforations on the web material. A preferred embodiment of the invention incorporates the indicator device on a film cartridge to provide an indication when the film strip moves out of the cartridge. The preferred embodiment addresses at least one of the aforestated problems, i.e., the problem of knowing when the film leader is not properly engaged with the take-up spool, and the film is not seen to be advancing properly.
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