US Patent 8409039 Dual stage clutch

Continuously variable speed drive (CVT) have improved performance due to use of two groups of flyweight cams, each group being mounted on separate rotational members of a centrifugal clutch. One set of flyweight cams provides force to close the sheaves through the entire movement of the shift, whereas the other set of flyweight cams provides force only through an initial portion of the shift and then signs off. This provides a two stage shift behavior for the CVT that enhances power transfer to the driven pulley.