Patent ID: 6094543
Filing Date: 2000-07-25
Classification: G03B

Abstract:
A sprocket wheel adapted to be rotated by movement of a photo film, said photo film having plural perforation sets arranged along one edge thereof in line at a regular pitch, each of said perforation sets including first and second perforations separated from each other by a first distance, a distance separating immediately adjacent said perforation sets being greater than the first distance, said sprocket wheel comprising:at least one tooth set including first and second teeth, said first and second teeth being positioned on the sprocket wheel so that the first and second teeth may simultaneously be in mesh with said first and second perforations, respectively;at least one contact face for frictionally contacting a portion of said photo film between first and second perforation sets, to be rotated by said movement of said photo film, said first and second perforation sets being included in said plural perforation sets and adjacent to each other, said tooth set being meshed with said second perforation set after being disengaged from said first perforation set;a wheel body; andat least one arc-shaped arm, formed on said wheel body, disposed close to a periphery of said wheel body to form a gap therebetween, shiftable resiliently toward a rotational center of said wheel body, an outside of said arc-shaped arm having said contact face;wherein said second perforation is larger than said first perforation, and said second tooth is larger than said first tooth;wherein each said first tooth is disposed on a respective said arc-shaped arm.