Variable ratio drive pulley

An infinitely variable drive pulley for a belt drive transmission, said pulley comprising a shaft that carries opposed first and second frusto-conical flanges adapted to accommodate between them a drive belt, said first flange being axially fixed on the shaft, said second flange being arranged on the shaft so as to be moveable in the axial direction thereon against the force of at least one return spring, said pulley including centrifugal weights in the form of adjusting levers, each said lever being pivotally mounted on a pin that is carried at a fixed position relative to one of said flanges, each said lever defining a cam surface that is adapted to engage a follower that is fixedly related to the other said flange, each said lever being so disposed that upon rotation of said pulley a centrifugal force is generated to press said cam surface into engagement with said follower with a pressure that increases with the speed of rotation such engagement applying a force that urges second flange to move axially towards said first flange against the force of said return spring, wherein an adjustable eccentric member is interposed between each said lever end its associated pin, said eccentric member being angularly adjustable to effect variations in the position of said lever relative to said pin in a plane normal to the axis of said pin.