Pulley having progressively variable sheave angle

A constant variable transmission comprising:

• a drive shaft rotatable about an axis of rotation;
• a pulley sheave assembly mounted on the drive shaft including
• a fixed flange supported for rotation on the drive shaft and having a first inner surface, and a movable flange, which is supported for rotation on the drive shaft and axially movable on the drive shaft toward and away from the fixed flange, having a second inner surface that faces the first inner surface, wherein at least one of the first inner surface and the second inner surface is disposed at a progressively variable angle with respect to a reference line that is perpendicular to the axis of rotation and follows an arc having a variable radius,
• a biasing mechanism disposed adjacent to the movable flange that displaces the movable flange with respect to the fixed flange, and
• a belt coupled to a drive mechanism and disposed around the drive shaft between the fixed flange and the movable flange, wherein the movable flange engages the belt and the belt moves across the first and second inner surfaces based on transmitted torque.

A method of transmitting drive force from an engine to a drive assembly while varying a drive ratio between a drive pulley assembly coupled to the engine and a transmission belt coupled to the drive assembly, including:

• providing a drive force to a rotatable shaft;
• transferring drive torque from the rotatable shaft to a drive pulley assembly having a fixed flange and a movable flange and moving the movable flange toward the fixed flange;
• engaging a transmission belt between inner facing radial surfaces of the fixed flange and the movable flange;
• and
• varying the drive ratio between the belt and the drive pulley assembly by sliding the belt across the inner surfaces of the fixed flange and the movable flange, wherein the inner surfaces are disposed at a progressively variable angle with respect to a reference line perpendicular to the axis of rotation of the rotatable shaft and follow an arc having a variable radius.