Lens-fitted photo film unit and sprocket wheel for the same

摘要

Photo film has plural perforation sets arranged along one edge thereof in line at a regular pitch. Each of the perforation sets includes first and second perforations, which are arranged closely at a regular distance. A sprocket wheel is rotated by movement of the photo film. The sprocket wheel has a wheel body. Two tooth sets respectively include first and second teeth, are disposed to protrude from a peripheral face of the wheel body, and are respectively meshed with the first and second perforations serially. An arm is disposed on the peripheral face of the wheel body, for frictionally contacting a portion of the photo film between first and second perforation sets, to be rotated by the photo film. The first and second perforation sets are included in the plural perforation sets and adjacent to each other. Each of the tooth sets are meshed with the second perforation set after being disengaged from the first perforation set.