sprocket
noun [ C ] engineering specialized uk/ˈsprɒk.ɪt ˌwiːl/ us/ˈsprɑː.kɪt ˌwiːl/ (also sprocket wheel)
链轮;输片齿轮
a device like a wheel with one or more rows of tooth-like parts sticking out that keeps a chain moving on a bicycle or pulls film, paper, etc. through a machine