Abstract: A sprocket mechanism for cameras includes a sprocket consisted of a body and a raised annular portion, a positioning plate fitted onto the sprocket, and an electrical switch located near the positioning plate. The sprocket body has two opposite pairs of pawls spaced suitably apart, and the raised annular portion has two notches provided at predetermined positions. When the sprocket rotates through 180 degrees, the electrical switch is caused to be on or off. A motor is caused to stop after an electrical signal is detected. At the same time, it can be determined that a frame of the film has been advanced and precisely positioned, and a counter is provided to display the number of frames advanced.

Abstract: A sprocket mechanism for cameras adapted for advancing a film provided with two juxtaposed sprocket holes at regular space intervals includes a sprocket with a body having a couple of pawls spaced apart at a pre-determined distance at a circumferential rim thereof and a first gear disposed on a top side of the body and having a notch at a suitable position thereof, a transmission gear having a second gear formed on its top side, the second gear having a shaft extending from a bottom side thereof and being inserted into a central hole of the first gear, the shaft capable of free movement within the central hole and having a stop element fitted thereon, the stop element being provided with a vertical segment at an extreme end thereof to be retained in the notch of the first gear. When the pawls of the sprocket engage the sprocket holes of the film, the sprocket, the transmission gear and the stop element rotate synchronously.